Biological aspects

Due to its appearance, aloes resemble cacti, but in reality their botanical genus (Aloe) has traditionally been classified in the Liliaceae family, along with garlic, onion and asparagus. The English researcher Tom Reynolds (2004) later considered them as a new family: the Aloáceas. At present, they belong to the Xantoroeáceas, subfamily Asfodeloideas, monocotyledonous plants native of temperate to tropical regions, usually of arid habitats of the old World: the Mediterranean Basin, Africa and Arabia. The most conspicuous genus of the family is Aloe, formed by perennial, xerophytic and succulent plants, that is, they adapt to habitats with low or erratic availability of water. Physiologically, It is characterized by the ability of its species to store large volumes of water in the interior plant tissue, as well as to use the acid metabolism of crasulaceae (Crassulacean acid metabolism, also known as CAM photosynthesis), by which photosynthesis adapts to the physical conditions of arid climates. . The aloes have green and fleshy leaves covered by a thick cuticle or bark and a clear inner pulp where the water is stored. The bark of the leaf represents around 20-30% of the total weight of the whole plant and the pulp, about 65-80%. The physical-chemical composition of aloes differs according to species and varieties, climate and growth conditions. Most species of the genus Aloe form dense annual inflorescences, in panicles or clusters, with small tubular flowers of yellow to red color. But the Aloe vera flower should be cut, thus avoiding pollination, which would give rise to hybrids with properties different from the species of origin. Therefore, it is preferable to reproduce it by cuttings, a method of asexual multiplication that is also very prolific for this species, thus preserving the genetic purity of the population. Aloe barbadensis var. Miller is a acaule species or very short thick stem (maximum 10 cm) from which sprout in rosette, extended or ascending, from 10 to 25 greenish leaves and lanceolate towards the apex to about 30-60 cm in length, with serrated margins, a width at the base of about 5-8 cm and an average thickness of 1 to 3 cm, the latter very linked to the humidity conditions. Only a few species of aloe have commercial importance, Aloe vera being considered as the most potential in terms of the production of gel and acíbar. The root system consists of a main root of 5-10 cm long and about 5 cm in diameter, which in turn is made up of several (5-15) secondary roots from which as many tertiary rootlets originate. The aloe vera plant has an inflorescence in the form of a simple cluster or compound, capable of containing 100-200 (or more) hermaphroditic flowers, small and reddish-yellow in color, arranged helically on an erect scale of approximately 90-100 cm in length that springs from the center of the basal rosette. Initially, the flowers take an ascending direction toward the apex of the inflorescence, being pendulous at maturity. The gynoecium is formed by three welded carpels and has an ovary superior of three lobes, all surrounded externally by six free stamens with long filaments that start from the floral base. Both the calyx and the corolla consist of three colored pieces. The fecundation of the flower produces a dry, capsular and elongated fruit, whose pericarp opens naturally (dehiscent walls) to let out a great variety of very small hybrid seeds, so for its cultivation it is convenient to cut the escapo. The little fruit formation in Aloe barbadensis Miller suggests that, in addition to the lack of synchronization between the maturation of pollen and the receptivity of stigma, there is a complementary mechanism of self-incompatibility that would limit sexual reproduction in this species. On the other hand, the main stem generates rhizomes that can give rise to other daughter plants next to the mother base, a characteristic that allows it to acquire, in its natural environment, very extensive and compact forms. This asexual multiplication is usually avoided by the aloecultor, separating and tearing off the shoots and replanting them separately to obtain new plants. 3.1. Leaf structure By giving a cross section to any mature aloe vera leaf, you can clearly distinguish three types of tissues (layers), which from the outside to the inside are: the cortex or skin, a thick layer of green color that protects and envelops to the pulp; the channels for the distribution of water and (peri-cyclic tubes), a yellowish and bitter juice; and the pulp, where is the gel of aloe, a crystalline substance and constituted mainly by water, since its dry matter is less than 1%. 3.1.1. External layer or bark It gives solidity to the leaf and is composed of multiple interspersed layers of flexible and resistant cells with chloroplasts that form a leathery epithelial tissue. The stomata allow liquid and gaseous exchange with the outside, while the cells are synthesizing the organic components needed by the plant: carbohydrates, fats and proteins. 3.1.2. Fibrous layer or conductive tissue In the interior of the pulp, just below the bark and adjacent to it, vascular bundles are arranged as small sheaths. The number of such beams varies according to the size of the leaves and their age. This layer is composed of three types of tubular sheaths: a) Xilema: which transports water and mineral salts from the roots to the leaves. b) Floema: distributes the organic materials made in the leaves to the rest of the plant. c) Peri-cyclic tubes: store and transport the acíbar to El acíbar, a compound rich in aloin, is popularly known as “sap or aloe juice”, being used by the pharmaceutical industry as an active ingredient to make laxatives, although its function biological is to protect the plant against possible predators (animals), due to its bitter taste. As already indicated in the history chapter, the word aloe has an Arabic origin and probably refers to the acíbar. 3.1.3. Pulp or heart Technically, the pulp is the fleshy part of the leaf, where the cell walls and organelles are included, while the mucilaginous substance (gel) is all the viscous liquid located inside the parenchymal cells. This layer, the largest in volume of the leaf, is formed by a spongy cellular tissue, through which the crystalline and aqueous mucilage (gel) is produced, where most of the active principles of aloe vera are located, which protects the plant from any cut produced on the leaf. The carbohydrates obtained during photosynthesis in an amount higher than necessary are transported by the phloem to the parenchymal cells of the pulp, being stored there. Water, mineral salts and malic acid, an organic substance formed in the metabolism of CAM plants, are also transported to the pulp, which serves as a hydraulic and energy reserve for the plant. 3.2. Photosynthesis Within the general characteristics of Aloe vera it is necessary to highlight its special way of carrying out photosynthesis, which is defined as a physical-chemical process of the plants by which the inorganic matter of the environment and solar energy (light) is used to synthesize organic compounds essential in the growth, development and reproduction of the same. From atmospheric carbon dioxide (CO2), mineral salts and water (H2O), the plant is able to synthesize sugars in the presence of sunlight, with oxygen (O2) release in the reaction. Although the plants present diverse forms of metabolic action, in this work we will not enter to study them different biochemical processes that are carried out in them, but we will say that there are three types: C3, C4, and CAM. This last route, the one used by Aloe vera, is the one that interests us here. The C3 metabolic pathway is found in most photoautotrophic organisms, while the C4 and CAM pathways are only in some vascular plants. CAM plants have a high degree of adaptability to the environment, where their anatomical and physiological modifications make them much more efficient than those of type C3, for the better use of water and energy. It is in arid environments with severe water deficiencies, whether constant or seasonal, where the CAM plants work as authentic specialists in optimizing the use of water, being able to reduce their growth rate in favor of survival. Quite the opposite would happen if the growth conditions were unbeatable: plant production would be very high. Another type of adaptation of plants with CAM metabolism, and that increases the water efficiency of those, is the ability to store water in its plant structure, being called crass plants, such as Aloe vera. The succulent tissue allows the water reserve contained therein to circulate throughout the plant during periods of drought. To capture the water they usually have a very developed root system, but not in depth but superficially. CAM plants have the ability to open their stomata at night and close them for the day, thus minimizing water losses in the plant. It constitutes, therefore, a more adaptive mechanism and an ecological advantage in places where water disposal is a limiting factor. All these adaptations make CAM plants efficient in the face of climates and environments with water deficit, while at the same time Some tolerance against severe water stress to which they can be subjected in one way or another. 3.3. Biochemistry of the gel The biochemical study of aloe vera, mainly with chromatography and electron microscopy techniques, has allowed the identification of the main components of the gel. This interest lies in its already known therapeutic properties. As already indicated in previous lines, the gel is a crystalline and mucilaginous substance that is stored in the pulp of the Aloe vera leaf. It has a water content greater than 99% and an acid pH (around 4.5), depending on these values ​​of the abiotic factors: water, temperature, light, humidity, soil, etc. The high acidity of the gel can be due to the storage of organic acids in the cells of the pulp, such as malic acid. Many researchers have tried to establish the active principles of Aloe vera gel. His biochemical analysis has revealed that lipids (5%) and proteins (9%) represent the smallest fractions of their dry weight. On the contrary, the content of soluble sugars (28%) and ash (23%) is relatively high. The minerals that most predominate are sodium and potassium, whose respective function is water distribution and tissue repair. Finally, the compounds of greater proportion are non-starchy polysaccharides, linear chains of molecules formed by glucosemanose, and lignin, which represent 35% of the dry matter. The size and structure of said polysaccharides cause the aqueous solution of the succulent tissue to increase its viscosity and opacity. 3.4. Varieties Aloe vera as it is known worldwide today, corresponds to the species Aloe barbadensis, a name adopted for abounding this plant on the island of Barbados, despite being native to the north-east African coasts. The species has been classified into three varieties: 3.4.1. Miller or vulgaris Name adopted in honor of the Swiss taxonomist H. Miller, who dedicated himself to the study of this variety imported by Portuguese merchants. Miller called it vulgaris because of its great abundance compared to the other two existing varieties. Of great commercial performance, its expansion took place from Arabia to Morocco, passing through the Canary Islands and Cape Verde. Currently, it is also grown in many countries of the American continent. 3.4.2. Humilis Native to South Africa, It was named for its smaller size, with small and elongated leaves of a bluish green color. Its smaller size is less productive than the vulgaris variety. 3.5. Other species of the aloe genus Making a botanical distinction of the genus Aloe according to its stem and leaves, there are three large groups: acaules (1), with a reduced but visible stem (2) and a broad, branched stem (3). The first group includes the aloes of soft and very short stems (not visible) covered with leaves forming groups of rosettes, to which belong the species barbadensis, aristata and saponaria. The second division is composed of plants with a woody stem and short, but visible, where A. succotrina, A. chinensis, etc. are included. By last, The third group is composed of aloes with woody and branched trunks forming bushes that can reach several meters in height, as happens with A. ferox, A. arborescens, etc. 3.6. Ethnobotany Ethnobotany studies the relationships between human beings and plants, its main objective being the knowledge about plants and their utilities in traditional daily life, constituting this link a popular culture, an intangible heritage, that should not be forgotten . The use of aloe vera in folk medicine is very old. It has been used effectively as a purgative, healing, cholagogue (stimulates the expulsion of bile), etc. Bitter acíbar is used as a digestive laxative or reconstituent, and the gel is applied to the skin to cure eczema, burns, etc. His current employment is more linked to manufactured products (gel, creams, shampoos, etc.). Finally, the species is also used to decorate parks, gardens, road roundabouts, etc. In the domestic sphere, besides being an ornamental plant, it is practical to have aloe vera grown in a pot, as it is a great healing remedy.

Edaphoclimatic conditions

Aloe vera plants have great adaptability in terms of height above sea level, soil class and climate. They have a better development in those hot and dry climates with temperatures of 18-40 ° C and heights of 0-1500 meters above sea level, reaching up to 2,500 m. On the other hand, the low temperatures, the excess of humidity and the badly drained lands affect considerably its development, being able to cause the necrosis of the leaves and the root. 4.1.Soil Soil is a mixture of organic and inorganic solids, air, water and microorganisms. All these phases influence each other: the reactions of solids affect the quality of air and water, which in turn wears out the former, and microorganisms catalyze many of these reactions. The physico-chemical properties of the soil that affect the development of the roots and, consequently, the growth of the plant are its depth, texture (see table 4.1), soil pooling, salinity and nutrient content. Aloe vera, as we can see, is undemanding to the fertile richness of the substrate where the plantation is located, being a very versatile plant that can grow both in terregosos terrains, as rocky or stony. 4.1.1. Depth. Morphologically, the depth of a soil is defined by the appearance of the parent rock. However, the useful depth for the proper development of Aloe vera roots should be considered. In general terms, a minimum useful depth would be between 50-60 cm, since its roots tend to expand superficially. 4.1.2. Texture The optimum edaphic texture for the cultivation of Aloe vera is that of loamy soils with high percentages of sand and silt (25-50%) and little clay (10-25%). These proportions generate physical-chemical advantages: better aeration, ease of working (sand), resistance to compaction, good drainage and at the same time good capacity to retain water (clay) and fertilizers. But this retention force is not very high, which allows the plant to take the nutrients dissolved in the soil. For this reason, they are the most appropriate textures for most agricultural crops. Also, Aloe vera prefers deep soils, somewhat calcareous, slightly acidic and with sufficient humus, while soils with an absence of calcium (Ca 2+), thin, basic or with little organic matter, They can slow down the growth of the plant. 4.1.3. Flooding The high sensitivity of the species to the excess of water makes its textural requirements regarding the flooding of the soil high. Aloe vera requires a soil with good drainage qualities, that is, a light and well-aerated texture that does not produce undesirable waterlogging, which would cause a decrease in the yield of the plant (growth, volume of the leaves, etc.) or even the death of it, especially when the plant is still young. The small inclinations or slopes of the terrain always favor this drainage, although if the textural conditions of the soil are suitable, the plantation can be located on flat land. 4.1.4. Salinity Soluble salts are present in all soils and provide essential elements for the growth of plants. However, in excess they can cause considerable damage and be a limiting factor for the establishment of the plantation. Therefore, it is necessary to analyze this factor by determining the total content of soluble salts by the values ​​of the electrical conductivity of the saturated soil extract (CEes). For the Aloe vera plant this value is between 8 and 10 dS / m, which corresponds to a good tolerance towards salinity. 4.1.5. Nutrients Aloe vera is undemanding to the fertile richness of the substrate where it vegetates and has a very high soil adaptation capacity that gives it the property of being able to develop on any type of soil, from infertile, poor or marginal soils to those very rich in organic-mineral matter. But the optimal edaphic conditions previously expressed are not an impediment to implement the cultivation of Aloe vera in any other soil type, even in those with high percentages of stoniness or extreme pH levels (acid and alkaline), since it is a species very adaptable to the agro-environmental conditions. On the other hand, the more the soil differs from the optimum, the plant will grow more slowly. The aloes do not grow on marshy areas, but in arid areas that are not suitable for other crops. 4.2. Climate Originally, the first areas of cultivation of Aloe vera were the great arid extensions influenced by the Mediterranean climate, like the whole basin of the same name (North of Africa, Spain, Italy …) and the southern part of South Africa. In this type of habitat the aloes had, apart from a lot of light, enough water so as not to have to resort to their reserve. Aloe vera is a plant that prefers a dry environment of temperatures between 18 and 40 ° C, rain regimes of 400 to 2,500 mm / year and relative humidity between 65-85%. However, although it survives well, during a prolonged drought it does not grow unless water is added (irrigation). For this reason, the cultivation of aloe requires an irrigation installation so that the plants continue to grow during the less rainy season. For the development of its leaves, Aloe vera requires an optimum temperature between 20 and 25 ° C. Although it supports the high summer temperatures well, the plant may suffer a delay in its growth if those are prolonged over time. It does not tolerate prolonged frost (<-2 ° C) or sudden changes in temperature between night and day. Due to its biological characteristics, Aloe vera adapts very well to unfavorable agro-environmental conditions for its cultivation. This versatility has meant that, despite being originally a crop associated with arid or semi-arid Mediterranean climates (Fig. 4.2), nowadays its cultivation has spread throughout Asia, Europe, Africa, Oceania and America, in subtropical climate zones where its warm-wet variant is given. These new territories conquered by Aloe vera have become true specialist areas in cultivating the plant, currently being the great exponents of world production. Some countries producing Aloe vera in the world are: Mexico, United States, Spain, Italy, Venezuela, Dominican Republic, South Africa, Chile, Israel, China, India and Australia. Generalizing, it could be said that almost all of them present, among others, a subtropical or Mediterranean climate.

Propagation

Los aloes, como cualquier otra especie vegetal, se originan a partir de una planta progenitora o madre. La reproducción sexual implica la creación de flores en donde se desarrollan los gametos, que tras la fecundación originan el cigoto, que madura hasta formar la semilla. Sin embargo, también pueden reproducirse asexualmente, bien empleando métodos de propagación vegetativa o por esquejado. En ambos casos, el genotipo de la planta madre se preserva, dando lugar a individuos genéticamente iguales o clónicos. 5.1. Reproducción sexual La planta de Aloe vera contiene los órganos femeninos y masculinos en la misma flor, pero sin embargo no se auto-poliniza, es decir, que necesita de al menos otra planta para fertilizarse, usando el polen ajeno de una sobre sus pistilos. Tampoco funciona entre plantas esquejadas, es decir, entre una madre y sus hijuelos, siendo necesario tener dos plantas genéticamente distintas. Sin embargo, este procedimiento sexual de propagar la especie no se utiliza en la práctica dada la ocurrencia del fenómeno de hibridación. Además, la plantación así cultivada sería poco eficaz y de un interés económico reducido para el aloecultor. 5.2. Multiplicación vegetativa La propagación vegetativa o asexual del Aloe vera es rápida y fácil, siendo realizada por medio de retoños o hijuelos que se desarrollan alrededor de la planta, los cuales pueden ser trasplantados directamente sobre la tierra de cultivo. Para efectuar una nueva plantación se utiliza generalmente la propagación por hijuelos obtenidos de otras plantaciones o reproducidos en viveros especializados. Los retoños pueden separarse cuando tengan al menos 20 cm, presenten la forma de roseta característica de la planta madre y posean también raíces bien desarrolladas, si no su aclimatación y posterior crecimiento serán más lentos. La primavera es la mejor estación del año para llevar a cabo esta operación, aunque si la plantación está en riego puede realizarse durante cualquier mes. Para impedir la formación de plantas híbridas, como efecto de la posible polinización por parte de otras especies, hay que cortarlas flores del aloe una o dos veces al año. Cuando los rebrotes alcanzan una altura de 20 cm pueden separarse ya de la madre, si no sus hojas perderían verticalidad. De todos modos, hasta los trece años puede sobrevivir una planta adulta sin acusar sensiblemente una reducción de su productividad. Los hijuelos pueden ser plantados directamente o introducidos en bolsas de polietileno para ser almacenados en vivero. El desahijado es una labor necesaria que favorece a la planta madre, además de al agricultor (beneficios por venta), ya que se pueden generar competencias por el agua y los nutrientes del suelo. La propagación clonal por cultivo in vitro constituye uno de los métodos biotecnológicos que mayores logros ha dado a un sinfín de cultivos agrícolas. Actualmente, se aplica en la producción masiva de plantas hortícolas, aromáticas, medicinales, frutícolas, ornamentales y forestales. Aunque Aloe vera se propaga de forma vegetativa en su estado natural, su tasa de propagación resulta ser demasiado lenta para la producción comercial de plántulas. Por ello, el cultivo in vitro de tejidos de Aloe constituye una opción biotecnológica para conseguir la propagación clonal rápida del cultivo, recomendada para especies vegetales que presentan bajos índices de multiplicación, logrando así la producción masiva de hijuelos libres de cualquier patógeno que pueda inhibir el desarrollo y posterior aprovechamiento económico del cultivo. Es posible la regeneración in vitro de Aloe vera empleando, por ejemplo, un medio de cultivo constituido por sales minerales, vitaminas, agar (0,7 %), sacarosa (6 %) y ácido indolbutirico (1 mg/l). Para desinfectar el tejido vegetal se recomienda utilizar un 3 % de hipoclorito sódico (NaClO) durante 10 minutos en agitación constante.

Cultivation techniques

In order to cultivate Aloe vera, a series of tasks must be applied throughout its vegetative period, all of them aimed at getting the plant to develop with the best possible agronomic conditions so that its productions are the most optimal. The main problem that farmers have faced when implementing Aloe vera has been the lack of publications dealing with their cultivation, despite the fact that in recent years the number of researchers interested in their agri-food and medicinal properties has grown. As a consequence of the low agroeconomic profitability obtained in other traditional crops, many farmers have decided to plant Aloe vera to increase their income per hectare, which has notably increased the world surface cultivated by this plant, but not yet cover the total demand. It is still pending the realization of scientific researches oriented to the improvement of the cultivation techniques that allow to advance towards the optimization of the production and the quality of the product. The actions to increase the profitability and the use of Aloe vera can be summarized as follows: – An improvement plan should be implemented for cultivation techniques that optimize production and product quality, as well as perfect postharvest techniques. – It is essential to increase the studies of selection and improvement of the species, as well as the propagation techniques of the same. – Research should be encouraged in industrialization processes (products of food, pharmacological, cosmetic interest, etc.). ) and disseminate the benefits that the plant has for society. All this will allow the use of the highest quality sheets. – Finally, it would be advisable to create Denominations of Origin of Aloe vera, as a fundamental element to defend a quality standard in the integrated areas, which will undoubtedly have a positive effect on producers and consumers. Next, the traditional cultivation techniques that have been used by the aloecultores will be considered. 6.1. Land preparation Although it is not a very rigorous species in terms of soil preparation, Aloe vera plants need a soil with good structure, so it is necessary to maintain the appropriate physicochemical and biological conditions. to prevent soil erosion. For it, any system can be used where it is possible to create an adequate medium that ensures certain rooting and contributes to the growth and development of the plants. Before starting the plantation, it is advisable to carry out a physical-chemical analysis of the soil that is to be cultivated with aloe, in order to know its nutrient levels and the improvements that can be made. The time to carry out this analysis can be a month before preparing the ground to establish the plantation. If traditional irrigation (flooding) is carried out, it is necessary to level the surface of the plot where the planting is planned, which will not be necessary if a localized irrigation system is used. The first thing to do is a deep work of the soil to dislodge it, by means of a pass with mouldboard or disc plows. This will serve to incorporate weeds and residues from the previous crop into the soil, as well as to favor soil ventilation. However, in the last two decades soil management has evolved towards a conservation agriculture (minimum tillage), avoiding turning and using implements that perform vertical tillage, such as the chisel plow (“chisel”). Then, you have to give a couple of passes with a grower, among which you can apply a background fertilizer (organic amendment) if deemed appropriate. This tracking will serve to undo the existing lumps of the previous operation. The number of passes with the grower will depend on the soil (texture) and the moment in which this work is carried out, being convenient to do it when the clods of earth crumble easily when tightened by hand, since if done afterwards they can be dry and will require one more harrowing step. The subsequent opening of the holes can be done on furrows (boards) or on flat ground. The asurcado is carried out with a specific implement attached to the tractor, called a mulcher or conformer. In very inclined terrain, the asurcado is carried out following the contours of level, with what the losses by erosion are diminished and a better distribution and aprovechamiento of the water of rain is obtained. It is preferable, in order to obtain highly developed and of the best possible quality (gel and acíbar), that the sowing holes have organic matter, already incorporated with the bottom fertilizer. The preparation of the soil should begin 45 days before starting the actual plantation and taking into account that the different tasks to be performed should be done when the soil is not too wet or dry, but in tempero. But in many places, as Venezuelan researcher HJ Piña Zambrano mentions, the aloe vera is cultivated with hardly any previous preparation of the land, based on a simple deforestation, if necessary, and in an ahoyado to be able to carry out the subsequent sowing. young. For this reason, it is important that a change of agronomic attitude occurs in future breeders, in order to obtain first level plantations that give leaves of high quality and with an economically profitable weight for the producer. From a technical and environmental point of view, the minimum tillage (conservation agriculture) is recommended, as it is the midpoint between the direct plantation with “no-till” and the traditional tillage (tipping, grading …), although there are also farmers (Tamaulipas) who prefer to continue with the intensive use of machinery for soil preparation before planting. 6.2. Plantation Having a shallow root system, the plantation of Aloe vera is a simple task, which is carried out by means of vigorous shoots with a year of life and a length of 20 to 25cm. Two types of suckers can be used: those that, once unfixed, have been stored in the shade outside of the ground and do not have an “active” root or those rooted from a nursery. In the first case, once the plantation is done, the youngsters take a brownish color, since, due to the lack of a developed radicular system, the plants will not be able to extract food from the soil and will maintain their own moisture until they reach water stress, at which time the roots will begin to develop. These suckers should not be irrigated until they have taken root. The suckers from the nursery should be transplanted directly to the final plot. To do this, the aloe seedlings are removed from the bag or pot and are immediately placed in the planting holes, which will be covered with soil to the rosette (foliar base). Finally, the so-called plantation irrigation is carried out. In both cases, the ahoyado presents about 20 cm of depth and dimensions in the groove of 20×20 cm, where each sucker is buried to the base of its leaves, then ramming all the earth around the plant to avoid leaving air pockets and thus avoid possible root rot. In addition, it is advisable to fix the Aloe vera crop on slightly inclined soils so that the plants can more easily drain excess water from rain or irrigation. On the other hand, high slopes would favor the erosion of the land. In the design of the plantation, it is also necessary that there is ease to remove the leaves at the time of harvesting. Therefore, it is advisable to leave streets with a width of three to four meters every 15 rows for the free circulation of tractored trucks or trailers that will be used during the harvest. Apart from the streets between rows you have to leave a path in the headlands, across the cultivation lines, also for the exit and entry of vehicles. 6.2.1. Planting season If you have an irrigation system, the plantation can be practically carried out during any month of the year. However, for those cultivated in dry land, the plantation should be carried out when the first spring rains begin, a season in which Aloe vera begins its annual growth cycle (leaf development). 6.2.2. Planting framework The number of aloes per hectare can vary depending on the geographical location (climate, slope …), physical-chemical conditions of the soil (pH, drainage …), etc., ranging between 2,500 and 25,000 plants, depending on the if it is grown to produce gel or acíbar and if the plantation is temporary (dry) or irrigated. One of the main factors to take into account in the cultivation of Aloe vera is sun exposure, since the plant needs a high annual luminosity for its good development. In rainfed plantations and inclined lands, the frame is 2 meters between rows and plants, with which a plant density of 2,500 plants per hectare is obtained. In the case of a land with very slight slope (plain), the distance between plants can be reduced to 1 meter, increasing the density to 5,000 plants per hectare. In irrigated plantations, the maximum yield of leaves per plant takes place with the minimum frame of 80 cm between rows and 50 cm between plants, equivalent to 25,000 individuals per hectare. On the other hand, the harvesting tasks for this frame are difficult due to the length reached by the leaves of the aloe, which reach up to 60 cm long. Thus, an advisable grid of plantation could range between 80×80 cm and 1×1 m, equivalent to 15,625 and 10,000 individuals per hectare respectively, thus facilitating the work of cultivation (weeding, harvesting …) and the proper development of the leaves. 6.3. Irrigation Irrigation is a compulsory technique in those areas traditionally dedicated to the cultivation of Aloe vera, also allowing high yields in the production of leaves. As it is a succulent plant, it is very resistant to the lack of water and, in general, to drought, so before returning to water it is convenient that the soil is dry. If it is watered frequently, the excess of humidity originates decay in the root and the leaves. On the contrary, the lack of water causes the aloe plant to consume its own water resource stored in the entire leaf volume, which manifests itself in the fact that the leaves appear folded inwards. All this indicates the versatility of the Aloe vera crop, capable of taking rainwater or watering and storing it in its leaves, increasing their volume and weight, being able to use this water resource for their own subsistence should any occur drought or running out of water in the irrigation well. For a correct programming of the irrigation it is necessary to know quite accurately the amount of water that must be applied, as well as the most suitable irrigation time and the most suitable method to use in order to make a homogeneous distribution of it. 6.3.1. Irrigation water quality Aloe vera, like permanent perennial or deciduous crops, It is usually more sensitive to poor quality irrigation than annual herbaceous crops. Irrigating water with poor agronomic qualities can increase the salinity in the soil, affecting its permeability, as well as causing damage to cultivated plants by accumulating toxic ions in their plant tissues, such as sodium, chlorine, boron, etc. To evaluate the quality of an irrigation water there are several empirical indices (Scott, CSR, etc.) of generalized use, through which we will obtain an indication of the possible problems to be taken into account for the subsequent decision making. 6.3.2. Water needs In order to develop an adequate irrigation recommendation, it is necessary to know the climatology of the area, especially the data of solar radiation, temperatures, rainfall, humidity and prevailing winds. The edaphological characteristics of the soil also influence, which determine the greater or lesser amount of available water and the difficulty with which the plant extracts it. As a general rule, it is recommended to carry out few irrigations but frequent during the summer season. In the case of flood irrigation, it can be applied every 20-30 days, with light sheets of 10 to 15 cm, although everything will depend on the type of soil in which the plantation is carried out. To avoid direct contact of the plant with moisture, keep it in the upper part of the furrow (ridge or board), ensuring that the water does not reach the leaf base, which would negatively affect the root. In the case of using the sprinkler or drip irrigation system, widely used in those producing areas with certain agro-technological development, an annual average of 100 liters per plant must be applied (4-5 irrigations per year). On the other hand, it is necessary to cut the irrigation between 15 and 20 days before collecting the leaves, since the transforming industries require a minimum content of solids in the gel. 6.3.3. At what time do you have to water? Traditionally, the method usually used for watering has been based on the experience of the aloecultor himself, that is, “by eye”, which has proven to be quite inaccurate. However, with the technification of the crop began to use other more objective methods based on the measurement of different edaphoclimatic parameters with specific instruments (rain gauge, tensiometer, etc.). On a practical level, the methods currently used are those that measure the matrix voltage of the soil by tensiometers, ceramic or plaster blocks, etc. On the other hand, the technique of controlled deficit irrigation does not apply in the cultivation of Aloe vera, mainly due to the lack of scientific research regarding the same species. Irrigation has been practically null in the cultivation of Aloe vera, being in very recent plantations when it has begun to incorporate irrigation by sprinkling, oriented towards the production of leaves for the use of gel. The frequency of the irrigation depends mainly on two factors: the type of soil and the climatic conditions (temperature, humidity, winds …) that predominate. When you have soils with less than 30% clay and more than 30% sand, irrigate every 15 days, while in the case of franc-clay soils, the waterings can be spaced once a month. However, when daily temperatures exceed 30 ° C, it is necessary to monitor the soil moisture and not wait for it to dry completely. For this purpose, a tensiometer can be installed to measure the extractive pressure of soil moisture on the part of the plants (see section 6.8.1). An aloe vera plant with enough moisture will produce a new leaf every 15 days, which means it will have six harvest leaves each quarter. However, when the plantation suffers from lack of water, leaf production decreases by half and acquires a very low weight. 6.3.4. Irrigation systems The ideal irrigation system is one capable of efficiently applying the water, installed at a minimum investment cost, require few maintenance tasks and have a reduced energy expenditure. 6.3.4.1. Irrigation by flooding It is the oldest system and, currently, one of the most used in agriculture. It requires a good ground leveling, with slopes lower than 1% and a large water flow, of the order of 1.6 liters per second to cover one hectare. Its main advantage is economic, since on relatively flat land it is possible to install this system with a low cost. Also, maintenance costs are moderate. The most important disadvantage that presents is the difficulty to apply water efficiently, because percolation losses can be raised at the beginning of the irrigation tables, especially if the soil is sandy. If water is a limiting factor for cultivation, Because aloe vera is sensitive to ponding, it is better to choose another irrigation system. 6.3.4.2. Irrigation by furrows This type of irrigation, along with the flood, make up the so-called irrigations by gravity. Like its counterpart, it requires a good ground leveling, although not as precise, with slopes lower than 2% and a water flow around 2-1.6 liters per second and hectare. This system is suitable for soils where water penetration is slow. The advantages and disadvantages turn out to be similar to those presented by flood irrigation. 6.3.4.3. Sprinkler irrigation This is the irrigation system most used in the large producing areas of Aloe vera. It is widely used in areas of irregular topography, not leveled, or in uneven or porous soils, with an excessive or inadequate infiltration rate. On the other hand, if the availability of water is limited, or if it requires an anti-frost protection, sprinkler irrigation is adequate. For its operation, it needs a continuous aqueous flow equal to 1 liter per second and hectare, much lower than gravity irrigation. Among its main advantages are the following: avoids excessive losses by percolation and allows a good uniformity in the distribution of water. On the other hand, the main drawback would be the high economic investment required for its initial assembly. In addition, the irrigation water must have low salt content, since it could be deposited on the stalks and cause considerable damage. 6.3.4.4. Localized irrigation (drip) This last system is based on applying small volumes of water and at low pressure, by means of drippers (emitters), in a reduced volume of soil and with a consumption much lower than any other type of irrigation. The flow of water in the drippers varies depending on the pressure, and may be between 2 and 8 liters / hour, although there are self-compensating that provide a fixed flow regardless of pressure variations. The system must have the capacity to supply the maximum daily demand in less than 16 hours, in order to have time for checks, breakdowns, traffic jams, etc. The main advantage of drip irrigation is that it allows watering if water is scarce -or this turns out to be expensive-, if the topography of the land is irregular or if the permeability of the soil is inadequate for other types of irrigation. The most noticeable drawback is the obstruction of the drippers by the soil particles and / or by precipitates of organic and inorganic material that can carry the water. 6.4. Fertilization Any plant needs to take from the soil mineral elements that are indispensable, in adequate proportions, to achieve its normal development. When the soil has deficiencies in some essential element for a given agricultural crop, its plant production decreases. These deficiencies can be corrected, in many cases, by simple addition to the soil of compounds containing said element, that is, by the addition of fertilizers. Fertilization is, together with irrigation management, one of the agronomic variables with the greatest influence on plant production, both in quality and quantity, of almost any agricultural crop, especially if both tasks are performed jointly: fertirrigation. An optimal NPK fertilizer can accelerate the growth of the plant – both its aerial (leaves) and underground (root) -, modify the nutritive composition of its plant tissues -with effects on the water reserve-, make it more resistant against water stress, diseases or cold; In short, it can affect all the quality attributes that are traditionally considered in the agronomic characterization of a plant. The edaphic texture should be taken into consideration when fertilizing, since a clay soil has more nutrients than a sandy soil. For this reason, the latter will have to pay more and, for this, slow-release fertilizers are especially recommended – a name that refers to their capacity to transfer, in a regular way over time, the mineral nutrients to the substrate-, such as zeolite, calcium sulfate, phosphorite …, which better counteract the possible losses due to leaching due to rain or irrigation water. Fertilizers can be organic (manure, ash, compost, earthworm humus, etc.) or inorganic (NPK complex mineral fertilizers). Nitrogen stimulates the bud and invigorates the development of the leaves. On the other hand, phosphorus stimulates a better structuring and expansion of aloe shoots, being also important to strengthen their roots. Finally, potassium strengthens the cellular structure of plants, giving them greater resistance to drought and invasions of phytopathogens. In its first year of life, the nutritional requirements of Aloe vera are mainly nitrogen. From the second year, after the first cut, the proportion of nitrogen must be lowered and potassium applied, in the form of potassium salt or potassium sulfate, if the soil needs it. It is recommended that phosphoric fertilization be applied right at the time of planting, in the form of natural phosphate. However, there are few scientific publications dealing with nutrient needs and fertilization in Aloe vera. Researchers A. Rodríguez, E. Molina and F. Chavarría (1996) indicated, for a cultivation of aloe in Guanacaste (Costa Rica), that the best fertilization dose, in kg / ha, corresponded to 150 kg of nitrogen (N ), 200 kg of phosphorus (P2O5) and 240 kg of potassium Both organic and inorganic fertilizers are important to ensure the proper development of the plants, They are elements that are completed to provide the ideal soil fertility. On the other hand, in organic cultivation of Aloe vera is recommended the use of organic fertilizers, such as animal excrement (sheep, goats, cows) or humus, which have provided good results. The application of chemical fertilizers is contraindicated by accumulating traces or mineral residues in the leaves, which is rejected internationally by the industries that use this raw material (HJ Piña). But the organic fertilizers, when presenting low content of nutrients, have to be applied at very high annual rates, around 20 and 40 t / ha, or be supplemented with mineral fertilization from natural sources. Aloe vera plants take about 2-3 months to form their first true roots, so during its first trimester of culture it will hardly absorb nutrients. Once the bottom fertilizer has been made (organic amendment), it is recommended to wait about six months to re-fertilize. During the following years, it is convenient to apply 5 to 10 t / ha of animal manure (manure), especially during the rainy season and / or after cutting leaves (harvesting). In plantations of aloe cultivated under nitrogen deficiencies there is a scarce foliar growth and a peculiar symptomatology: reddish leaves with necrotic apices in the oldest ones. The lack of phosphorus is also observed by a reduction in growth, but the bright green coloration of younger leaves and apical chlorosis in mature ones is the most evident visual indication. Potassium deficiency, in addition to affecting growth, causes the basal necrosis in the oldest leaves, while the young retain a blue-green color and grow curved towards the ground. 6.5. Cultivation protection Aloe vera is a species that tolerates heat and the incidence of sudden warm winds. On the contrary, the plant is more vulnerable to frost (cold environment). When intense frost occurs at temperatures below freezing (<-2 ° C), the pericyclic tubes and the coenchymal cells of the mesophyll are broken, introducing the anthraquinones into the gel. These tubes take on a dark brown color due to the increased pigmentation of the anthraquinones, causing a reddish coloration of the leaves. To avoid loss of quality in the gel by frost, the only option is to resort to the protection of the crop by means of thermal blankets. 6.5.1. Thermal blanket The thermal blanket can be extended manually or mechanically, as an agricultural film, along each row of plantation. Due to its low weight (17 g / m2), it must be handled with care so that it can be used in the next period of frost. When placing the thermal blanket should always leave a margin, both on the sides and above the furrow, to allow the free and safe growth of plants. In addition, it must always be placed according to the predominant direction of the winds. The tissue needs to be fixed at the extremities at regular intervals, which can be done with stones and / or by pouring a shovel of earth every meter. Another option to place the thermal blanket is in the form of a micro-tunnel, a system that allows a more adequate ventilation of the crop. As a supporting structure, Arched wires with a semicircular shape and variable width are used, whose diameter fluctuates around the meter. The most used material is galvanized iron, in rounds that usually have a caliber of about 4-6 mm. The arches are separated from each other at a distance of 1 meter. You can also resort to traditional materials, such as wicker, rods, etc. For a greater fixation of the micro-tunnel can be used ropes, stakes, etc. 6.5.2. Packing With this practice the planting with a plastic sheet is covered totally or partially (one or more rows). For this, polyethylene is used mainly and, in some cases, also PVC or even copolymers. In the cultivation of Aloe vera partial padding can be carried out, which consists of covering only the plantation lines with a plastic sheet (film) whose width does not exceed one meter. The use of mulch allows to increase the temperature of the environment close to the plant, which accelerates the growth of Aloe vera, obtaining a higher production. It also achieves a better use of irrigation water, since the waterproof plastics are both water vapor and the watery liquid itself, the temperature is maintained for longer, especially when an adequate management of irrigation is carried out; In short, the strong variations of humidity in the soil can be avoided more easily. Sandoval and Durán (2005) demonstrated the improvement in the growth and development of the aloe with plastic sheet, either transparent or opaque, providing a greater height of plants, the increase of the temperature of the soil and a lower symptomatology of damages by frosts, in comparison to when quilting was not used. The placement of the film can be done manually or mechanized. In the first case, an operator is gradually unrolling the plastic spool, while two others are reinforcing the sides of the sheets. But there are already agricultural machines capable of opening gutters so that their bottom lodges the longitudinal ends of the sheet as it unrolls. Later, some discs fill the open gutters with dirt, leaving the plastic fixed on the surface of the ground. Next, the planting of young people would be carried out. Finally, if opaque plastics are used in the light, an effective system to control weed infestations can also be achieved. In rural areas where labor is relatively cheap and there are hardly any frosts, this mulching can be replaced by manual weeding [see Ch. 7). 6.6. Desahijado The separation of the suckers that are born around the mother plant serves to avoid competition for water, light and nutrients among themselves, since when they are not removed in a timely manner, they detract from the quality of the leaves. This operation must be done at least once a year, when the suckers have a minimum length (height) of 20 cm, although if you want to use them to establish nurseries it is necessary to let them reach approximately 25 cm. Once the sucker is obtained, it must be stored in the shade for about a week or more so that the wounds produced in its start up from the mother plant will heal. Then they can be transplanted to individual pots or in the field of cultivation (new plantation). Over 18 months of life, the Aloe vera plant generates a maximum of two shoots, sometimes only one, while from the second and subsequent years it produces an average of four to five cuttings, which allows to expand the plantation at minimum cost . It is recommended to extract the leaves annually, after each leaf cut (harvest). If the root of the mother plant is uncovered when removing the shoots, it should be covered immediately to avoid further losses due to dehydration or growth retardation. Also, you should not water during the first two weeks after the victim, so that the natural healing of the wounds occurs. When being cut from their mother plant, the children can be some time out of the earth, about two years, since they are able to survive in a good state of conservation by healing the damaged part of the stem and roots. 6.7. Nursery The agronomic purpose of a nursery is the obtaining of plants that are homogeneous and free of phytopathogens with a greater adaptation to the environment where it is desired to carry out the plantation. This is the only way to obtain quality plantations. Once separated from the mother plant, when they are about 25 cm high, the children should rest in the shade for a couple of weeks in a dry and ventilated place, since they should not be watered or exposed to the sun for proper vegetable healing. Subsequently, they are transplanted to nurseries in different ways: bags, plastic pots, etc. The substrate to be used must be a mixture composed of 50% earth, 25% sand and 25% organic matter. After two months, in which period the seedlings have been acclimatized, they can be transplanted to the final plot. 6.8. Other tasks 6.8.1. Humidity control Soil water content can be found directly using edaphic samples (auger) or indirectly using a specific instrumentation: tensiometer, neutron probe, TDR … Today, the most commonly used method is the use of tensiometers, devices that measure the suction or force exerted by the soil on a volume of water. The tensiometer is basically a sealed tube filled with water, equipped with a vacuum gauge and a porous terminal capsule. To operate the capsule, and with it the rest of the tube, on the ground up to about 30 cm deep. Then, the vacuum gauge can already record the tension at which the water from the soil surrounding the tensiometer is located. As the earth loses moisture, the water in the pipe tends to exit through the porous porcelain end, thus lowering the water level of the apparatus and producing a relative vacuum in the upper part of the same, which is registered by the manometer. When the soil Normally, at least two tensiometers are used, one superficial in the area of ​​greater radical concentration, which allows to visualize the volume of water available for the crop, and another deeper to control the water depth of the irrigation. In general, the function of indicating the irrigation frequency is attributed to the surface tensiometer, and to the deepest to calibrate the irrigation time. 6 8 2. Coite floral (“crop”) Another work of cultivation is the cutting of the inflorescence that springs from the mother plants, cutting it from its base. Aloe plants should be prevented from developing their inflorescences, otherwise the vigor of aloe leaves will be reduced, mainly decreasing their volume. A practical way of suppressing the floral stem or quiote would be to wait for the escapes to rise above the leaves (Fig. 6.11) and before they bloom they cut at their base. otherwise it would detract from the aloe leaves, mainly decreasing their volume. A practical way of suppressing the floral stem or quiote would be to wait for the escapes to rise above the leaves (Fig. 6.11) and before they bloom they cut at their base. otherwise it would detract from the aloe leaves, mainly decreasing their volume. A practical way of suppressing the floral stem or quiote would be to wait for the scapes to rise above the leaves (Fig. 6.11) and before they bloom they cut at their base.

Weed control

In non-cultivable areas, Aloe’s own physiology and anatomy make it adapt to very adverse weather conditions where most weeds can not survive. But what is analyzed here is the herbaceous control in agricultural areas cultivated with Aloe vera. When competing for water and nutrients, weeds are a limitation for the cultivation of Aloe vera, since they reduce the yield of the crop, hinder the work of cultivation, reduce productivity and favor the proliferation of pests and diseases. Weeding is a normally manual task that has been applied since the beginning of the cultivation of Aloe vera. This practice is usually done twice a year, one of which precedes the collection of leaves. Some of the weeds most commonly identified in the different agro-ecosystems of Aloe vera, according to the region where the plantation is located worldwide, are: – Among the monocotyledons, white straw (Chloris polydactyla) predominates, among others; Lent grass (Digitaria sanguinalis), grass (Cynodon dactylon), chives (Cyperus rotundus), purple straw (Leptochloa filiformis), Johnson grass (Shorgum halepensis) or chicken feet (Eleusine indica). – Among the dicotyledonous include, among others, the cardo-santo (Argemone mexicana), the edge barrel (Salsola kali), the poppies (Papaver spp.), The tomatillo (Physalis ixocarpa), the purslane (Portulaca oleracea), the coquito (Cyperus rotundus), the little bells (Ipomoea spp.), the field mustard (Sinapis arvensis), the parrot (Amaranthus hybridus), the pumpkin (Cucumis anguria), the dry love (Bidens pilosa), the mallow (Malva parviflora), etc. The control of the weeds is common for the different agro-systems of crop (dry land / irrigated land), being especially critical in the plantations with installation of irrigation. There are two factors that regulate weed populations: endogenous, such as intraspecific competition, and exogenous, such as the effect of climate. Regulated plant species are more likely to move to other agricultural areas and invade them, as a result of being more resistant to climate change. Traditionally, manual control of weeds using husks has been carried out, being very careful not to damage the roots and stems of the aloes. In irrigated plantations, this work must be done permanently, otherwise the herbaceous plants would grow until they exceed the aloe plants, while the rainfed crops usually do it before each harvest and after a period of abundant rains. In young plantations it should be taken into account that an excessive development of weeds can cause staining (yellowing) of the lower leaves due to the lack of light (plant competition), as well as delays in the development of the aloes and in the production of children. Weed control can be carried out by applying various methods. 7.1. Manual procedure As already indicated above, manual cleaning is done around the plant, using husks, manual pruners, etc. It can also be assisted with the passage of a walking tiller with manual feed, if the size of the plants and the distance between rows allow it. But to control the weeds next to each aloe plant it will be necessary to resort exclusively to manual weeding to avoid damage to the plantation. In general, this operation will have to be carried out every 4-6 months. It is recommended to carry out at least four manual weeding per year, which may vary depending on the density and development of the weed. 7.2. Grazing The use of ovine animals in the plantations of Aloe vera can be an effective method provided that the animals have available water. In addition, it must be verified that the plantation is healthy, thus preventing the spread of diseases in it. 7.3. Mulch This technique is based on placing various materials on the surface of the soil to reduce water loss, improve its structure and minimize the growth of weeds. Recently, the crust of crushed aloe, a by-product in the transforming industries, has begun to spread, inhibiting sunlight and, consequently, the emergence of weeds. There are two main types of mulch: inorganic and organic. Among the first ones, volcanic stone, geotextile materials or powdered rubber stand out. Regarding their characteristics, it should be mentioned that they do not decompose quickly, so they do not need to be replenished frequently. On the contrary, they do not improve soil structure or add organic matter. Due to these reasons the aloecultores prefer organic mulches, which include wood shavings, pine leaves, bark of trees, aloe shells, vegetable remains, etc. They are subjected to a continuous decomposition, having to be replaced according to the material. This process improves the edaphic quality and its fertility, reason why many aloecultores consider this quality beneficial, in spite of its continuous maintenance. In general, a mulch with a thickness of 5 to 10 cm is recommended, since an excess could be detrimental to the cultivation of aloe, the main drawbacks being: – The increase in humidity, which could cause decay of roots. – Modification of pH in the soil. The proper management of this technique would be to check if the soil drainage is adequate to apply a thin layer of well-spread mulch. 7.4. Chemical control It is important to clarify that chemical herbicides should not be applied in the control of the weeds developed in ecological aloe crops, since they would alter the quality of the final product (acíbar or gel) due to the facility that has the plant to capture the active principle thereof. Although the use of herbicides in organic farming is not allowed, there are farmers who practice this control, so it is recommended to use this product in the early stages of cultivation with planned applications to avoid the direct contact between the plant and the chemical poison as much as possible. . The use of any herbicide must be suspended during the four months prior to harvest, thus avoiding undesirable chemical residues in the raw material. since they would alter the quality of the final product (acíbar or gel) due to the facility that has the plant to capture the active principle of the same ones. Although the use of herbicides in organic farming is not allowed, there are farmers who practice this control, so it is recommended to use this product in the early stages of cultivation with planned applications to avoid the direct contact between the plant and the chemical poison as much as possible. . The use of any herbicide must be suspended during the four months prior to harvest, thus avoiding undesirable chemical residues in the raw material. since they would alter the quality of the final product (acíbar or gel) due to the facility that has the plant to capture the active principle of the same ones. Although the use of herbicides in organic farming is not allowed, there are farmers who practice this control, so it is recommended to use this product in the early stages of cultivation with planned applications to avoid the direct contact between the plant and the chemical poison as much as possible. . The use of any herbicide must be suspended during the four months prior to harvest, thus avoiding undesirable chemical residues in the raw material. Therefore, it is recommended to use said product in the early stages of cultivation with planned applications to avoid the direct contact between the plant and the chemical poison as much as possible. The use of any herbicide must be suspended during the four months prior to harvest, thus avoiding undesirable chemical residues in the raw material. Therefore, it is recommended to use said product in the early stages of cultivation with planned applications to avoid the direct contact between the plant and the chemical poison as much as possible. The use of any herbicide must be suspended during the four months prior to harvest, thus avoiding undesirable chemical residues in the raw material.

Pests

Aloe vera plants can be attacked by certain pests, which will depend on the geographic territory where the plantation is located. These pests can feed on their inner gel or on the outer bark. However, if the cultivation conditions are adequate, that is, with a soil rich in mineral elements, adequate irrigation, good ventilation, etc., it is difficult to have this type of problems. This chapter aims to provide an overview of the most frequent pests that can attack the plantations of Aloe vera, such as aphids, red spider, woodlice, whitefly and caterpillars, also explaining the measures that must be taken to counteract these possible attacks 8.1. Aphid (Aloephagus myersi) This is an aphthous insect with a soft body, so it is easy to fight. They feed on the sap of aloe by sticking a sucking beak into its tender leaves, causing important damage to young plants. Part of the sucked sap is excreted as sugary liquid (molasses), which impregnates the surface of the plant preventing the normal development of it. Aphids can be winged or apterous and their color is very variable, ranging from white to black and going through green or yellow. As for their reproduction, they are parthenogenetic, that is, females can have offspring without being fertilized by males, thus proliferating in large numbers. The climatic conditions that favor its development are the high temperatures and a low relative humidity. 8.1.1. Symptomatology and damage Normally, leaves infested with aphids are deformed, curled or wrinkled. They are also betrayed by the presence of the black (Capnodium elaeophilum), a fungus that sits on molasses. It produces two types of damage: direct and indirect, giving the first when it feeds on the juices that transport the phloem of the plant, as they alter the growth hormones and, in general, weaken the plant. As for the indirect ones, they derive from the animal metabolism, that is, the excretion of molasses that is then colonized by the bold, causing decreases in the photosynthetic capacity of the leaves and being able to transmit toxic substances or even phytopathogenic viruses. 8.1.2. Control The preventive control of aphids can be done through traditional methods, eliminating weeds, applying mulch, etc. When traditional control is insufficient, Low energy products, such as potassium soap, will be used to clean and save time. If this treatment is still not effective, other insecticides allowed in organic farming could be used, such as gelatin or vegetable and paraffin oils. It is also very useful to place yellow, gummed, and attractant chromium-tropic traps (pheromones), particularly for winged species. To fight against bold, you must apply lecithin or some copper fungicide (copper hydroxide, copper oxychloride …). Regarding biological management, this is based on the integrated fight against pests through natural predators of them, such as the ladybird (Cryptolaemus montrouzieri) or the praying mantis to fight this aphid (Aloephagus myersi). 8.2. Red spider (Tetranychus urticae) It is a very small mite that is almost not detected with human vision. They can be yellow, green or red, simple or compound (yellowish-green) with two black spots on the back. They appear when conditions of high temperatures and very dry environment occur. They feed on the cellular juice of the plant tissues they parasitize, by sucking it through bites that they cause with their buccal apparatus. Infections begin in the spring with mites fresh from hibernation, which last for successive generations from summer to autumn. When days shorten and temperatures drop, females migrate to hibernation (winter). 8.2.1. Symptomatology and damage In Aloe vera, The first symptoms of the attack by red spider are small red or yellow points on the underside of the leaves, while the strongly attacked ones take a yellowish color and they become scarce assuming an almost dusty aspect until they end up detaching (defoliation). Analyzing more closely, you can also see subtle cobwebs, composed of fine fabrics of a silky thread, which is accentuated at the bottom of the leaves. The direct damage caused by this insect is mainly due to its demolishing action on the green parts of aloe, which pierce with a stylet. The loss of chlorophyll leads to whitish or yellowish speckling in the beam. The deterioration is more important the younger the plant is, causing a delay in its growth, thus decreasing the overall production and its quality. Large populations of red spider could even destroy a plantation completely. Its biological cycle is represented in Fig. 8.2. 8.2.2. Control The preventive control of mites can be done with traditional methods, such as the elimination of weeds, a balanced dose of fertilizer, etc. An excess of nitrogen compounds favors the proliferation of red spider. It can also be sprayed with water (nebulizations), since mites do not like humid environments. Only in the case of particularly serious infestations, sulfur can be used although paraffin oils are also very effective. The chemical fight should be started when the plague is detected, especially in the early stages of its development. The treatment must be directed to the infectious foci when they are well defined, paying special attention to the perimeter boundaries of the plantation, which is usually where the insect enters. As for the biological control, it is mainly carried out thanks to the predation made by phytoseiid mites: Amblyseius californicus and Phytoseiulus persimilis. 8.3. Cochineal cotton or honeydew (Planococcus citri) The different species of cochineal are characterized by having a protective shell of different colors and consistencies that vary from one specimen to another. Planococcus citri (Fig. 8.3 above) is a suction insect protected by a layer of dust with wax that its own body generates, which makes it difficult to combat them. They act by sticking a stiletto on the leaves of aloe to suck their inner sap (food), excreting part of the juice as a sugary liquid (molasses). They may have one or more generations in the same year, depending on the climate of the area. They hatch like larvae of eggs, transforming themselves into adult pillbugs that, in turn, lay more eggs, from which they re-hatch larvae forming a second generation. 8.3.1. Symptomatology and damage This insect is detectable with the naked eye in the foliar apices, by the presence of some cotton balls. They attack the entire aerial plant body but are more visible towards the tender parts (tips). It is also betrayed by the presence of the fungus Capnodium elaeophilum, which sits on molasses. It produces direct and indirect damage to aloe plants, the former manifest themselves in a loss of vigor, caused by the extraction of the pillbugs from the vegetable juice, and by the appearance of deformed, discolored, yellowish or dry leaves. As for the indirect, the settlement of the black oak on the excreted molasses causes a blackening of the leaf surface, with the consequent loss of capacity to carry out photosynthesis, which ends up weakening the aloe plant. 8.3.2. Control Pillbugs are insects that are difficult to fight because they have shells that protect them from insecticides. In the first instance, its control may consist in eliminating those parts of the plant that are very affected. In terms of chemical control, to be much more effective, it must be directed against the larvae, because they are more sensitive to insecticides than adult specimens. Once these are detected, a contact insecticide allowed in organic farming (rotenone) should be applied, repeating a posteriori if necessary. The effectiveness of the treatment will depend on whether it is done when the greatest number of possible larvae occurs (undeveloped population). On the other hand, if necessary, some copper fungicide should be applied to fight against the bold. It is advisable to control the possible re-infestations, since an absolute control of the woodlice is something very difficult to achieve. As a general rule, it is possible to carry out a preventive control of cochineals, applying an ecological treatment in spring, at which time the larvae begin to proliferate. Regarding the biological management of pests, the integrated fight against Planococcus citri can be done with the introduction of Cryptolaemus montrouzieri (ladybug), a natural predator very effective against an attack of aphids. 8.4. Cottonwood root bugs (Rhizoecus spp.) To detect mealybugs that parasitize the root system it is necessary to inspect the root ball. If these appear full of a white milkweed, they are cottony scale boll weevils (Fig. 8.3 below). 8.4.1. Symptomatology and damage It is not easy to detect this pest, but a symptom of its infestation is that the plant does not grow. If it is observed that some aloe plants have not grown at the end of spring, one should suspect the possible presence of Rhizoecus spp. Later, the plants will begin to turn yellowish and produce the death of some specimens in short periods of time. This plague lives on the roots of the plant, sucking its juices, which brings with it the destruction of the root system and, ultimately, the destruction of it. 8.4.2. Control The control is similar to that described for the previous case. As for the chemical treatment, the insecticide must be applied by means of irrigation so that the roots can reach it. 8.5. Caterpillars These are lepidoptera that during their caterpillar phase lodge in the younger leaves of aloe, and can cause a serious plant deterioration if they are not combated in time. 8.5.1. Symptomatology and damage Due to their great voracity, they produce serious damage to the leaves, where they are grouped destroying them completely. We must also highlight the damage caused by the bad smell of the excrement that accumulates between the inner leaves of the rosette. 8.5.2. Control If any caterpillar is discovered by the crop, it is not necessary to apply an immediate treatment, except when we are facing a very strong infestation, in which case it is recommended to treat with bacterial preparations made with Bacillus thuringiensis, forming an insecticide allowed in organic farming that does not require security deadlines. 8.6. Whitefly (Trialeurodes vaporariorum) These are small white flies that, like aphids and woodlice, stick a stiletto to aloe leaves and suck their sap. The blade is thus weakened by the injuries caused during drilling. They perch on the foliar surface (underside) by means of a peduncle that serves as a support. The optimal conditions for its development are high temperatures and humid environment, so its highest incidence takes place in summer. When the whitefly-infected aloe plants are shaken, they will fly off to form a cloud composed of hundreds of individuals. 8.6.1. Symptomatology and damage The first indications that demonstrate the existence of whitefly can be seen by observing its leaves, since they first yellow, then appear discolored and, finally, detach from the stem when drying. Also, the leaves are covered with molasses excreted by the hemipterans themselves, on which the bold stands. The direct damage is caused by both larvae and adults, sucking the sap of aloe, which paralyzes the leaf development and causes the fall of some leaves. From elsewhere, the molasses that the flies secrete is the seat for the bold, diminishing the photosynthetic capacity of the leaves. Yellow spots appear, discoloration and wilt. 8.6.2. Control Fighting adult flies is relatively easy, while fighting larvae is complicated due to the carapace they have during that state. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus. decreasing the photosynthetic capacity of the leaves. Yellow spots appear, discoloration and wilt. 8.6.2. Control Fighting adult flies is relatively easy, while fighting larvae is complicated due to the carapace they have during that state. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus. decreasing the photosynthetic capacity of the leaves. Yellow spots appear, discoloration and wilt. 8.6.2. Control Fighting adult flies is relatively easy, while fighting larvae is complicated due to the carapace they have during that state. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus. 8.6.2. Control Fighting adult flies is relatively easy, while fighting larvae is complicated due to the carapace they have during that state. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus. 8.6.2. Control Fighting adult flies is relatively easy, while fighting larvae is complicated due to the carapace they have during that state. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus. Among the preventive measures include the use of yellow chromatic traps and a balanced handling of nitrogenous fertilizers. In case of observing whitefly, chemical control can be carried out applying authorized products in organic farming. Regarding the biological control, it can be carried out favoring the proliferation of certain parasitic species of the whitefly, such as Encarsia formosa or Macrolophus caliginosus.

Diseases

The traditional cultivation of Aloe vera has not had diseases of great importance. However, in the present millennium, aloe plantations have been affected by numerous agronomic changes, sometimes bad practices, such as high density (intensive cultivation), the proliferation of weeds for not weeding, lack of selection and disinfection of suckers in transplants and a free exchange of raw material between different geographical areas of production (HJ Piña, 2009). All this has resulted in a higher incidence of diseases for Aloe vera plants. Thanks to the phytopathological studies carried out by international organizations and institutions, such as INIA Falcón (Venezuela), American Phytopathological Society (USA), etc., it is possible to identify the main diseases that attack the cultivation of Aloe vera all over the world. Among the most frequent are (according to HJ Piña and Z. Lugo): – Foliar spots caused by fungi: Altenaria sp., Cercosporidium sp., Phaecosphaeria nigrans, Physalosphora sp., Concentric Microsphaeropsis and Phyllosticta sp. – Stem rot produced by Phythium ultimun. – Root rot caused by Rhizoctonia solani, Phytophthora nicotianae var. parasitic, Phythium ultimum, Fusarium oxysporum and Sclerotium rolfsii. – Bacteriosis caused by Erwinia chrysanthemi. This chapter aims to offer an overview of the diseases that have a greater incidence in the cultivation of Aloe vera and, therefore, those that suppose a greater economic loss for the aloecultores. 9.1. Bacteria Phytopathogenic bacteria cause diseases that can affect, in principle, any cultivated plant and produce large annual losses throughout the world. To minimize them, it is necessary to know their survival mechanisms and their dispersion. The symptomatology they produce is extremely varied, but generally characteristic for a particular pathogen. Symptoms can vary from mosaics to large abnormalities, such as “gills” (Agrobacterium tumefaciens), but the most common are spots on leaves or fruits, blights or tissue death in leaves, stems or tree trunks, root rot or tubers, etc. All of them, can vary in turn with the photoperiod, plant variety, environmental conditions (temperature, humidity …), and the dose of infection. In some cases, the development of a bacterial disease may come to a halt when passing from one season to another, for example in Córdoba (Spain) from cold-wet winter to hot-dry summer, and may even disappear or become unimportant as the plant growth. 9.1.1. Soft rot (Erwinia chrysanthemi) All species of the genus Erwinia are pathogenic of plants. The causal agent of producing rots in the stem (bud) of Aloe vera is E. chrysanthemi, a flagellated and mobile bacterium of micrometric dimensions. This species occurs mainly on basal leaves, bracts or fruits of numerous food crops with great economic importance: banana, onion, pepper, corn, pineapple, carrot, etc. The favorable factors for the development of the disease are high temperatures (25-35 ° C), high humidity, both of the soil (waterlogging) and the environment, and an excess of nitrogen fertilizer. 9.1.1.1. Symptomatology The first symptoms may go unnoticed, but if the plant is analyzed more carefully, wet spots of soft appearance may be observed on the leaves, both at the base and in the lamina. Then, if the temperature and humidity are high, the tissue decomposes, taking a light brown color and foliar necrosis. The final result is a rottenness with a soft and malodorous consistency, which begins in the area of ​​the heart. If a very intense attack occurs, the Aloe plants wither, breaking most of the most tender leaves of the stem. 9.1.1.2. Epidemiology Erwinia chrysanthemi can survive in different types of soil, water, plant remains and roots of weeds. The penetration of the bacteria in Aloe vera takes place through wounds, being favored by the presence of water on the vegetable surface. The infectious process usually begins in zones close to the soil, being common in the wounds produced during the cuttings of the leaves (harvest) or the suckers. The diffusion can be carried out by wind, water, insects and man. 9.1.1.3. Control The fight against the soft rot of Aloe vera should be preventive, since once the bacterial attack is started it is very difficult to control, advising the cupric treatments. Preventive measures include avoiding excess nitrogen fertilizers, the irrigations by aspersion and a high humidity in the ground. 9.2. Fungi The diseases caused by phytopathogenic fungi in their hosts show a very diverse symptomatology, such as chlorotic and necrotic spots, sifting, cankers, blights, wet or dry rot, mummies, gills, dents, crusts, drownings, wilts and pustules. These fungi can be classified into three large groups: mucilaginous molds (Mixomycetes), pseudo fungi (Oomycota) and true fungi (Kingdom Fungi). 9.2.1. Leaf spots (Alternaria alternata) This is a filamentous ascomycete fungus that has sepidio and simple conidiophores, at the end of which conidia of brown color are formed with transverse and vertical septa of irregular disposition. By budding of the apical cell, long chains of ten or more conidia are generated, forming rapidly growing colonies. It is a common fungus in strawberries, tomatoes, carrots and asparagus, but it can also be found in fertilizers, woods and soils. 9.2.1.1. Symptomatology Leaves with a certain maturity can be observed foliar spots of different sizes, circular shape and brown color, from which concentric rings of darker color stand out.As the lesions evolve, the epidermis appears bulky. In the center of the bulges there is a scarce superficial and whitish mycelium, from which dark-colored structures emerge. The borders of the infection are delimited by an orange-purple band between two darker ones. Finally, strongly attacked leaves show a state of generalized wilt and die. 9.2.1.2. Epidemiology The fungus Alternaria alternata can live in a wide range of temperatures, although its development is retarded when it is in relatively cold environments. The indirect propagation of the fungus in the vegetal tissues of its host produces little mycelium on the epidermis, forming on the surface of the rotten area a small mass of mycelium that at first is whitish and then takes a dark color. 9.2.1.3. Control It is carried out mainly watching that the suckers are not infected by the pathogen (nursery). As for chemical control, it is done by spraying of fungicides allowed in organic farming, such as citrus seed extract, copper oxychloride or horsetail. Sprays should be started when the first injured plants appear, repeating each week in environmental conditions of high relative humidity and high temperatures. The latter should be reduced to once every fortnight if the fungus persists but the humidity conditions are reduced. 9.2.2. Powdery mildew The favorable conditions for the development of powdery mildew are temperatures around 25 ° C, stopping its growth at approximately 35 ° C. The germination of the conidia is favored by a relatively high humidity. It is produced by ascomycetes and ectoparasite fungi of different genera: Uncinula spp .; Erysiphe spp .; Sphaerotheca spp .; etc. 9.2.2.1. Symptomatology This disease is manifested by the presence of a whitish-white powder on the surface of the leaves, although it also usually affects the stem. Finally, the parts attacked by the fungus turn yellowish and wither. In Aloe vera this disease can seriously affect its leaves. 9.2.2.2. Epidemiology The fungus develops “prensores” with which it is fixed on the epidermis, feeding on its cells by means of haustoria. While the mycelium grows, upright structures appear (conidiophores), where the conidia will develop. The latter, once mature and in great quantity, end up detaching, thus constituting the ash that characterizes this disease. The transport of the spores of the fungus to another plant is done by wind dispersion. 9.2.2.3. Control Being a fungus with external development, it is very sensitive to sulfur fungicides, although its negative action on the beneficial fauna makes it contraindicated for biological control. It is important to treat with sulfur when there are temperatures below 30 ° C, because if you could not burn the leaves. On the other hand, vegetable extracts of cinnamon, horsetail, etc. are also applicable. 9.2.3. Standing evil (Pythium ultimum) It is a pseudohongo belonging to the Protista Kingdom [Oomycota], which parasitizes countless plant organisms and causes watery rot. This phytopathogen is characterized by its hyaline cenocytic mycelium (without septa) and thick mycelium, with bulges from place to place. In the mycelium spherical esporangia are formed, generally apical, of micrometric diameter. Its hyphae (vegetative cells) contain a single diploid nucleus and have walls rich in cellulose but without chitin, which distinguishes this organism from true fungi (Kingdom Fungi). 9.2.3.1. Symptomatology Depending on the age and stage of growth in which the plant is found, symptoms or others will appear. Hatchlings are attacked almost always at the level of their roots or, sometimes, at ground level. In the latter case, the affected aloes will present a strangulation at the base of the stem, and a soft brown rot may appear in this area, which will cause the plant to lose its support capacity and be “damping off” or drowning fungal) without losing the greenish color of the leaves. When attacked aloes are already adults, they almost always show small lesions on the stem that do not produce plant death unless the damaged area spreads to a deadly volume for the plant. 9.2.3.2. Epidemiology Pythium ultimum is an inhabitant of the soil that parasitizes many plant species, but it is particularly active in soils of clayey composition that retain water, a favorable circumstance for this phytopathogenic organism, especially if temperatures below 20 ° C are found. In its development it forms a whitish, filamentous, branched and rapidly growing cottony mycelium through which it can be identified. This mycelium generates terminal sporangia (asexual reproduction) of irregular geometry that directly produce germ tubes, behaving like true conidia, or form a filamentous and cenocitic hyphae at the end of which a vesicle is created where the biflagellate zoospores are produced. Sexual reproduction occurs by contact, through fertilization tubes, between the female gametes (oospheres) of the oogonium and the male ones of the anteridium, which for P. ultimum, having only one oosphere in each oogonium, it will give an oospore. The spore germ tube or the saprophyte mycelium comes in contact with plant tissue due to root exudates. The penetration takes place through slits by mechanical and enzymatic pressure. 9.2.3.3. Control Sometimes, some practices of traditional use are useful to reduce the level of infection. The most important factor to prevent this disease is to perform an adequate drainage of the soil. 9.2.4. Root and stem rot (Rhizoctonia solani) The name Rhizoctonia is derived from Greek and means “death of roots”, corresponding to an imperfect fungus of the Fungi Kingdom that does not form spores in its vegetative phase (sterile mycelium) and whose sexual reproduction does not exist or is unknown. This phytopathogen radicular (R. solani) is characterized by producing sclerotia, compact volumes of hardened mycelium with nutrient reserves to survive during extreme environmental periods, which originate strands capable of associating with the root system of a plant. These sclerotia allow the fungus to remain dormant at the underground level until its optimal conditions appear, feeding, meanwhile, the organic matter that the soil presents. The disease caused by Rhizoctonia solani appears more frequently during the wetter months of the year, because rainfall creates a humid environment in the soil, causing a more or less continuous growth of the fungus, especially at high temperatures (> 25 ° C). 9.2.4.1. Symptomatology Adult aloe plants affected by Rhizoctonia solani manifest primarily foliar chlorosis and, in general, a scrub of the leaves. Then dark spots (necrosis) will appear on the stem and roots, which in turn will cause decay in both organs (“damping off”), as well as the consequent leaf fall. If the roots are exposed, necrosis and necrotic plaques may be seen in them, as well as lumps due to the scarring produced at the junction with the roots and / or missing rootlets. 9.2.4.2. Epidemiology When the sclerotia of Rhizoctonia solani located in the soil of an agricultural plantation are activated, the first thing that the fungus must do is to cross the vegetable cuticle. For it, develops swollen hyphal structures that facilitate infectious penetration through a double activity: mechanical and enzymatic. You can also access through the injuries that are caused in the plant due to the passage of machinery, animal damage (herbivores) or the weather. In a plantation of Aloe vera, the fungus Rhizoctonia solani can access it by incorporating already infected foreign shoots and by the dissemination of sclerotia through agricultural irrigation or vegetable organic matter scattered in the soil. 9.2.4.3. Control Once the first symptoms have been developed, there is no curative treatment, so preventive measures should be taken to use agronomic techniques that mitigate the water imbalances that trigger the fungal attack. Among these measures can be highlighted: – Use a localized irrigation system (drip). – Moderate the use of nitrogen fertilizers, especially ammonia. – Add an organic manure, well prepared, to improve the structure of the soil, promote root development and increase the C / N ratio, thus strengthening the plant against the phytopathogens. On the other hand, for a soil already very colonized by the fungus, a high percentage of organic matter favor attacks on the crop, because, due to its high saprophytic potential, Rhizoctonia solani can survive in the form of mycelium on it for several years. . 9.2.5. Vascular wilt (Fusarium spp.) This fungal disease has been identified in almost all areas producing Aloe vera, with a high percentage of incidence on this crop. Among the ascomyceous fungi of the Fusarium genus that attack Aloe vera, F. oxysporum and F. solani have been recorded. The optimum conditions for the development of the disease are a high moisture content in the soil and high levels of nutrients, mainly organic matter, phosphorus and magnesium. In general, temperatures between 25 and 30 ° C predispose to infection. In addition, the symptomatology is worsened in drought conditions, since diseased plants, having their root system affected, suffer greater stress. 9.2.5.1. Symptomatology Vascular wilt is characterized by intense yellowing of the leaves, in addition to its thinness and curved towards the ground (flaccidity), easily detaching from the base. Another symptom in infected plants is that their growth and development are reduced compared to the others. On the other hand, when making a cross section to the root and / or the stem, reddish spots will be observed that later turn brownish-brown, indicating the destruction caused by the fungus in the vascular system of the plant, even reaching to produce death. 9.2.5.2. Epidemiology The fungi Fusarium spp. They are found on the ground as structures resistant to unfavorable conditions (chlamydospores), and may remain dormant for several years. The germination of these structures is stimulated by the exudates that the roots excrete, giving rise to germinative tubes that are attached to them. The penetration of the fungus into the plant is direct and occurs through the epidermis of the root apex, from where the fungal infection is transferred to the vascular system, producing conidia that are dispersed by the vegetal flow forming new colonies. The production of gummy substances causes blockages in the vessels of the xylem that hinder the rise of water and mineral elements from the roots to the aerial part, giving the plant a sickly appearance due to vascular wilt. The dissemination of the fungus occurs through water, work implements, agricultural machines, harvest remains and the implantation of infested suckers. 9.2.5.3. Control It is advisable to avoid injury to the roots, plant in well drained soils, do not irrigate excessively, etc. Among the most effective control methods to control vascular wilt caused by Fusarium spp., A physical procedure called solarization should be highlighted, that allows a gradual reduction of the phytopathogen in the infested soil. 9.3. Nematodes Nematodes are the most abundant group of multicellular animals in the soil that occupy the majority of habitats. Those phytoparasites represent a limiting factor for the production of diverse crops in the tropical and subtropical zone of the whole world. Their direct damage to roots and other plant organs, produce various types of symptoms: chlorosis, wilting of plants in warm hours of the day, decrease in yields, loss of commercial quality in roots / tubers and, in cases of high populations , the death of host plants that are very susceptible and not tolerant to these organisms (Z. Lugo). Most nematodes are difficult to observe in the soil because of their microscopic size and because they are translucent. The animal body is in an elongated, unsegmented tube that is tapered at the ends. The main characteristic of phytoparasitic nematodes is the stiletto, a structure used to “prick” the tissue of the host plant. 9.3.1. Helicotylenchus dihystera It is a microscopic nematode, elongated and spiral shaped. Areas of irregular growth appear in the plots affected by this phytoparasite. 9.3.1.1. Symptomatology The aloe plants infected by this nematode present a greater sensitivity to wilting due to water imbalances, they grow more slowly and the leaves take a yellowish color (chlorosis), discoloring towards the apex. If the population of nematodes in the soil is high, they can cause plant death. This symptomatology is nonspecific and similar to that produced by other root diseases or nutrient deficiencies, so confirmation of a problem by nematodes must be carried out through a soil analysis. 9.3.1.2. Epidemiology The second juvenile stage, infective, is free through the soil in search of host roots to penetrate them by mechanical and enzymatic action. Within the root system, the enzymatic secretion of juveniles induces the creation of “giant cells” through which the nematode feeds. Because of this, the vessels of the xylem are blocked and the formation of nodules in the root occurs. The establishment of the “giant cells” is essential for the juveniles to complete their life cycle, going through several changes until they reach adulthood. At that time, the male leaves the root while the female remains to reproduce asexually, depositing hundreds of eggs. (See Fig. 9.4). 9.3.1.3. Control The control measures should be oriented to prevent that the populations of the nematode reach a critical value for the plants and the farmer (economic damage), otherwise it would be necessary to apply organic-natural nematicides (oils of Ricinus communis or Azadirachta indica). It is not convenient to use chemical pesticides because they could exterminate, in addition to the phytopathogens, those beneficial nematodes for the plant and the soil. Among the traditional control methods include: – A deep tillage before implanting the aloe crop to provoke the exposition of possible plant remains (roots) to the heat and thus achieve its desiccation. – Apply organic matter because it causes an increase in the populations of antagonistic microorganisms of nematodes. – Disinfect farm implements. As for biological control, fungi are used, such as Paecilomyces lilacinus and Myrothecium verrucaria, which parasitize the eggs produced by the females at the root. 9.3.2. Meloidogyne spp. 9.3.2.1. Symptomatology Like many other nematodes, they do not cause characteristic symptoms in the leaves or aerial part of the plant. Aloes infected by Meloidogyne spp. they show yellowing, wilting and reduced plant production. Infection of the roots causes characteristic thickening or galls that can be of different sizes, depending on the number of females inside. 9.3.2.2. Epidemiology Normally, eggs of the genus Meloidogyne pass the cold season (winter) in the soil until the temperature increases (spring), at which time the second stage juveniles hatch to migrate through the land and penetrate the roots of some host plant. During their growth, the juveniles get fat and molt until their conversion into adult males or females. The adult females have a rounded and immobile body, while the males are filiform and generally leave the root when not feeding on it. The females produce bags that can contain more than 500 eggs within a gelatinous mass. Consequently, an aloe vera root infected by this nematode can harbor millions of eggs contained in all those bags. Generally, the gall-generating nematodes complete their cycle in less than a month, depending on the temperature of the soil and, therefore, may have several generations during a plant cycle. 9.3.2.3. Control First of all, it is necessary to prevent the entry of the nematode, because once it has been established it is virtually impossible to eradicate it. Therefore, it is important to use certified suckers and clean nematode propagation material. The plots infected by Meloidogyne spp. they should stay out of plant production for a period ranging from 2 to 4 years. Meanwhile, other crops resistant to the nematode can be used in order to reduce their population. Weeds must be eliminated to prevent them from being alternative hosts for nematodes. In general, those plots that have been cultivated with some plant species susceptible to the nematode Meloidogyne spp., Such as horticultural crops, should be analyzed before planting aloe to check the presence of gall-generating nematodes. In the event that the levels detected are above the economic threshold of damage, the use of organic-natural nematicides or alternative control methods, such as solarization and parasitic fungi of eggs (biological control), is recommended. 9.4. Pathophysiology In addition to bacterial, fungal diseases or those caused by nematodes, Aloe vera can be affected by other agents of abiotic origin, which produce deviations harmful to the normal functioning of their plant physiological processes. In general, these are difficult to diagnose conditions that are resorted to when the origin of the disease can not be attributed to any living being. 9.4.1. Excess of water A temporary flooding of the soil does not usually cause serious damage to the plants, but if it is prolonged in excess it can cause root asphyxiation, concentration of mineral substances at toxic levels for them, etc. In the case of Aloe vera, it is a crop very sensitive to waterlogging, excessive irrigation or temporary rains, whose symptoms may vary due to two factors: the level of humidity reached, especially in the roots, and the duration of the ponding. A lasting flood due to rain in aloe cultivation, can cause slow growth of the plants and the folding of leaves forming folds. But the most serious situation occurs with the development of fungi, belonging to the genus Pythium, Phytophthora and Fusarium, which cause diseases to plants (already studied) and significant economic losses for the aloecultor. 9.4.2. Water shortage When there is no water available, the leaves of Aloe vera are thin and folded inwards because it consumes its own internal liquid (water reserve). Therefore, this plant is very resistant to prolonged droughts. 9.4.3. High salt concentration A soil with high salt levels, for having used a saline water for irrigation and / or having been exceeded with the use of fertilizers, It can produce alterations to plants. Although Aloe vera plants are considered very tolerant to salinity, high salt concentrations can cause a decrease in their growth. 9.4.4. Effect of temperature Cultivated plants develop their plant activity between fairly wide temperature limits, which vary according to the species and stage of growth, with adults being more resistant to extreme temperatures than young people. The Aloe vera supports better high temperatures (warm-dry environment) than low temperatures (cold-humid environment), being the optimum value for its good development of 25 ° C. If there are high temperatures that extend over time (droughts), the aloe plant slows its growth to survive. For the case of continuous frosts over time, the leaves of aloe take a reddish coloration, caused by increasing the concentration of anthraquinones in the gel. 9.4.5. Effect of brightness and insolation Both excessive (insolation) and poor lighting can have a negative effect on aloe plants. Thus, with few hours of light, the leaves tend to be horizontal instead of vertical. On the contrary, although the aloe plant needs a high solar radiation, its excess causes the leaves to turn brown. The maximum saturation rate of sunlight for Aloe vera can be set at 850 μmol / m2 With few hours of light, the leaves tend to be horizontal instead of vertical. On the contrary, although the aloe plant needs a high solar radiation, its excess causes the leaves to turn brown. The maximum saturation rate of sunlight for Aloe vera can be set at 850 μmol / m2 With few hours of light, the leaves tend to be horizontal instead of vertical. On the contrary, although the aloe plant needs a high solar radiation, its excess causes the leaves to turn brown. The maximum saturation rate of sunlight for Aloe vera can be set at 850 μmol / m2

Harvest

The cultivation of Aloe vera is done to obtain the maximum possible volume of leaves, which can be cut by their base when they reach a certain minimum weight, which should not be less than 450 grams in irrigated land and 375 in dry land. In addition, for its commercialization, the raw material (leaves) must meet quality standards in its appearance and form, such as not being sick, having a good appearance in terms of color and vigor, not showing spots or physical damage, etc. When cutting the leaves of a rosette, the plant should be left with a minimum of four to six central leaves for the proper subsequent development of it. The time of cutting will be influenced by the existing climatic conditions, the agronomic status of the plantation, etc. For rainfed crops, the first short one usually occurs in the second / third year of having established the plantation, with a single annual harvest being carried out later, but two may occur in those years with abundant rainfall. In irrigated plantations, the initial harvesting is normally done a year and a half after having established it, and the number of annual cuttings can be varied from three to six and obtaining between four and six leaves per aloe plant for each cut. Another limiting factor during the harvest phase is cold, since frost can seriously damage aloe leaves, which support minimum temperatures of up to -2 ° C, decreasing the number of leaves to be cut. One month before carrying out the harvest, it is suggested to apply a cut of the dry leaves that are on the periphery of the rosettes. In both rainfed and irrigated plantations, harvesting is done manually with a sharp knife, making a chamfered cut at the base to prevent the plant from rotting, especially in rainy months. The cutting procedure follows the following pattern: first the blade is grasped with one hand, then two incisions are made on both sides of its base and, finally, a slight upward direction is made; thus, the leaf should come out complete and with a white callus on its base that serves as a seal to the leaf to avoid weight loss by dripping. A poorly done cut can lead to a rapid oxidation of the sheet, producing quality losses in the final product (transforming industry). Later, Harvested leaves should be treated with extreme care to avoid damage and reduced quality due to incorrect handling of the raw material. To do this, once cut, the sheets should be placed on wooden or plastic boxes, ensuring that the concave part of them is looking vertically upward. Likewise, it is recommended not to completely fill the boxes, since when superimposing one on top of the other in a crisscrossed way for later transportation, the leaves could be mistreated. It is also advisable to make the cut when the destination of the harvest is clear, since the interior gelatin of the aloe is easily contaminated and decomposed. In case of not having assured commercialization, the aloecultor could stop harvesting for a whole year without deteriorating the quality of the raw material (leaves). The last cut is made when the plantation reaches 10 years, or even more. The productive cycle of aloe vera ends when the leaves lose quality and volume due to wilting and spotting, due to the aging of the plants, an excess of moisture due to prolonged waterlogging or inadequate crop management. Once the productive period is over, if you want to continue with production, you have to carry out selective screening, tracking and transplanting. Sanitation pruning can also be carried out on the mother plants, replanting or leaving on the plantation those shoots that are better developed (thinning the mother plant). Depending on the density of the crop (planting frame), the leaf yield may vary. In rainfed, once the plant is already in full production, what happens from the second / third year, for 2. 500 plants per hectare and an average weight of 375 grams per leaf, the yield can range between 3,750 (1 short) and 7,500 (2 short) kg / ha. In irrigation, considering full production (from 18 months), a frame of 1 × 1 m plantation (10,000 plants / ha) and an average weight of 450 grams per leaf, you will obtain a yield that varies from 54,000 (3 short) ) to 108,000 (6 short) kg / ha.

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Aloe Vera Propagation

Aloe vera has multiple medicinal properties, being used to moisturize the skin, heal wounds and even as depurative. Getting one is really simple: in all nurseries and garden stores we can find specimens for sale, but … is there any way to get new plants without having to spend any money?

Although it is very economical (an adult specimen costs about 4 dollars), if we already have one it will not be necessary to disburse that money again, because it will not be necessary. Let us know how to reproduce the Aloe vera plant .

Seeds

Although it is not a method that is used a lot, as a curiosity and to acquire experience in the sowing of succulents it is very interesting to plant the seeds of our beloved Aloe vera plant . But, before planting them, you must first obtain them . And how is that done? Very easy.

As you can see in the image below, the flowers of Aloe are grouped in inflorescences. These are tube-shaped, yellow in color. As well. If you want to produce seeds, what you have to do is pass with a medium brush (slightly more than 0.5cm) for each of the flowers until you see that they “swell”  (something that will happen after a few days) ) twice each day. After a while, you will see that a kind of ball forms: it will be the fruit.

When it dries, it will be time to open it and extract the seeds . As these weigh very little, if it is windy it is very advisable to open the fruits in a room so that they do not fly away.

Then, you just have to plant them in a pot with substrate that has very good drainage , such as black peat mixed with pearlite in equal parts, leaving a distance of about 2 cm between them. Cover them with a very thin layer of earth (thick enough so that they are not directly exposed to the sun), and finally water.

They will germinate soon , after a week or fourteen days at the most.

Shoots

Multiplying Aloe vera by shoots is the easiest and fastest option. From a certain age (normally, two to three years after sowing) it will begin to produce small Aloe shoots that will sprout from the main roots , but sooner rather than later will have their own root system.

These plants are pups that grow very fast, to the point that you only have to wait a month until you can separate them from the mother plant. And when the time comes, it will not take much complication. What’s more, to remove them with root you only have to put on gloves, dig a little (about 5cm) on both sides of the sucker and, without taking your hand off the ground, pull it out .

Once you have it, plant it in a pot of about 10.5cm in diameter with universal cultivation substrate or with black peat mixed with 50% perlite, and water. As soon as roots come out of the drainage holes, you can pass it to a larger pot or the garden.

Aloe Vera Diseases

Aloe vera or Aloe Barbadensis Miller , which is also known as aloe vera in some countries, is a plant that is usuallygrown in areas with a subtropical or temperate climate , among which is included the Mediterranean and does not require a large amount of water to survive.

Thanks to its enormous amount of properties , aloe vera is a plant that is used for many products.

Most common Aloe vera diseases

We can also say that in the world there is an approximate of about 250 varieties of aloe , but that only two or three of these are those that possess all these properties.

In the same way that happens with the rest of the plants, aloe vera despite its resistance may be prone to attacks of certain pests and diseases , so today we will mention the most common.

Among the diseases and problems that can affect aloe vera we can mention the following:

Aphids

These are small insects belonging to the homoptera family , the size of these is quite small and its color may be different depending on which species. They are the cause of a great variety of serious problems due to the enormous proliferation they have, which means that they reproduce very fast.

The Mites

These are tiny insects that are usually a nightmare for plants, since they use all parts of the plant as their source of food , thus causing damage that is very serious and thus cause the death of the plant.

White fly

Although this small insect has wings , it can be quite harmful and feeds voraciously on aloe vera. The greatest amount of damage is produced by the eggs, as well as the larvae left by adult flies, and when they have the ability to fly they spread very easily.

Millet beetles or also called flour beetles

The name that these small insects have is due to the white color they have and they are usually confused with the woodlice although they are not. They use the triangulations of the plant as their food.

Treatment for aloe vera diseases

It is important that we can leave aloe leaves that are withered or have a yellow color, for that we can use a pruning shears . We must also remove leaves that are severely affected by insects.

Then we have to spray the plant with the help of a strong jet of water so that the remaining insect pests are eliminated completely.

Some of the pests mentioned above can be eliminated simply with water. The fungus gnats usually have their hiding underground, so if we have this plant in a pot or container, it is important that the turn away from other plants for so contaminated with insects.

Once this is done, we can remove the insects that are left with our hands . We can rub off the stems and leaves with the help of a cotton swab.

When we have already removed the insects from our path, we have to put a special tape to catch insects , which is the yellow adhesive, near the aloe vera plant so we can catch the flies as well as the mosquitoes in their adult stage .

Spray our aloe vera plant with an insecticide that is registered to be used in indoor plants and follow each of the instructions found on the label to know the dose of application .

This is a process that we must repeat at least every three or four days for a couple of weeks in order to eliminate insects in their adult stage that hatch after applying the aerosols. An oil spray can be of great help to eliminate the scale insects as well as scale insects, as this product is responsible for suffocating insects.

How To Recover Aloe Vera Plant

The Aloe vera is a non-cacti succulent plant that is relatively easy to care. So that it grows well, it needs a substrate that drains water well, a lot of light and regular watering. But sometimes problems can arise that we will have to solve to revive it.

Let’s see what those problems are and how to recover an Aloe vera plant .

HOW TO RECOVER ALOE VERA PLANT ? HEALTHY ALOE VERA IN A POT

Burns by the sun

The Aloe vera is a plant that needs to be exposed to sunlight directly about 3-4 hours a day, but of course if we buy at a nursery where they had protected and are exposed directly to the next day we see that has leaves with burns. But, however serious it may seem, it has a solution .

It is a very resistant succulent and to revive it we will have to put it in semi-shade , where it is protected from the sun king. If there are whole leaves burned, we can remove them to make it look better.

Excess irrigation

The symptoms of excess watering in Aloe vera are the null growth, rotten central leaves (and the rest soft), and there may also be fungi that are affecting it. If we want to recover it we will have to act quickly, and for this we will have to do the following:

  1. First, we will extract it from the pot and we will remove all the soil that we can.
  2. Then, we pulverize its roots with a systemic fungicide to eliminate the fungi that may be present.
  3. Then, wrap the root ball with a napkin or paper towels, and leave it like that for a couple of hours.
  4. Next, we take it off and plant the Aloe vera in a pot with a well-draining substrate, such as a pomice or black peat mixed with pearlite in equal parts.
  5. Finally, we put it in semi-shade and do not water until after a week.

Lack of irrigation

Recovering an Aloe that is going through thirst is very, very easy: you just have to water it . We will know if there is a lack of irrigation if we see that the leaves close, wrinkle, if there appear yellow spots that soon turn brown (starting with the tips) or if the plant does not grow at all.

So, once we know what is going on, we will take the pot and put it in a bucket with water for ten minutes . In this way, the soil will be well soaked and the roots will be able to hydrate the plant.

When To Plant Aloe Vera? Why Late Winter?

The Aloe vera is a succulent plant cactus not, or crass plant, well known for its many and varied properties. It is so much, that you could almost say that it has become a habit to take a piece of paper, open it and spread your gel for any wound we have done. But, did you know that, in addition to a pot, you can also have it in the garden?

If you have a piece of land, even a small one, you can have one or several copies of this wonderful plant. You just have to know when to plant Aloe vera in the garden . The answer you are looking for, we will give it to you right away ????.

The Aloe vera , known as aloe, aloe or aloe Barbados Curacao, is a succulent plant native to Arabia has achieved naturalized in subtropical and temperate regions around the world, including the Mediterranean. As you probably know, the leaves grow in a basal rosette, and they are green – only the youngest specimens may have whitish specks.

Although it is a plant quite resistant to cold and frost of up to -3 ° C , the best time to put it in the garden is in late winter , when the minimum temperature is 10 degrees Celsius or more. In the case that you bought it in the autumn and live in an area with a mild or frost-free climate, you can plant it at any time of the year, unless it is blooming; if it is, wait for its flowers to wilt.

Choose a place where you can grow without being directly exposed to the sun, and make a hole deep enough to fit properly. Now, remove it from the pot and insert it into the hole, and finish filling it. Finally, it will only be watered.

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