Orchid Diseases

In this article we will study thoroughly the different diseases and pests that can appear in an orchid along with their photos and symptoms so you can identify these orchid diseases easily. Also, we will describe the most suitable treatment to get your orchid cured. We will explain the most suitable treatment for diseases in the orchids Phalaenopsis, Dendrobium, Vanda, Cambria, etc

Below we present in a generic way the most common orchid diseases differentiated according to the causative agent. We must bear in mind, but, that these diseases can be presented together if there are the necessary conditions for it. 

For example, fungi and bacteria can attack simultaneously if there is excess moisture or poor ventilation. In turn, the presence of certain insects (aphids) can facilitate the spread of fungi.

Table Of Contents

  • 1 ENVIRONMENTAL CONDITIONS WHERE DISEASE APPEARS
  • 2 SIGNALS THAT YOUR ORCHID MAY BE SICK:
  • 3 PESTS / INSECTS IN THE ORCHIDS:
    • 3.1 Cottony orchids in the orchid (Coccoidea):
      • 3.1.1 Treating Orchids with Insecticides, eliminating cochineal:
    • 3.2 Aphids or aphids (aphids or aphids):
      • 3.2.1 Symptoms of aphid infection:
      • 3.2.2 Eliminate aphids from orchids and other plants:
    • 3.3 Mites
    • 3.4 Leafminer
    • 3.5 Red Spiders
  • 4 BACTERIAL INFECTIONS IN ORCHIDS:
    • 4.1 Bacterial Rot / Brown Rot – Pectobacterium – Diseased leaves of orchids:
      • 4.1.1 Symptoms:
      • 4.1.2 Treatment of bacteria:
      • 4.1.3 Prevention:
    • 4.2 Black rot – Pythium and Phytophthora:
      • 4.2.1 Symptoms:
      • 4.2.2 Treatment:
      • 4.2.3 Prevention:
  • 4 DISEASES OF THE BULB, STEM AND ROOT:
    • 5.1 Fusarium Want:
      • 5.1.1 Symptoms:
      • 5.1.2 Treatment of Fusarium Wilt in orchids:
      • 5.1.3 Prevention:
    • 5.2 Soilborne Fungus – Rhizoctonia:
      • 5.2.1 Symptoms:
      • 5.2.2 Treatment of rotten roots in orchids:
      • 5.2.3 Prevention:
  • 6 FUNGI IN LEAVES AND FLOWERS OF ORCHIDS:
    • 6.1 Antracnosis – Colletotrichum y Glomerella:
      • 6.1.1 Symptoms:
      • 6.1.2 Treatment:
      • 6.1.3 Prevention:

Environmental Conditions Where Orchid Diseases Can Appear

This chapter related to the environmental conditions that favor the appearance of orchid diseases is the most important of this long article.

If you get this right, you will not have to worry about orchid diseases as you will be able to prevent almost all the diseases that affect the orchids. So this paragraph is the most important.

The best way to keep orchid diseases at bay is to undertake preventive measures, and one way to prevent is to take care of and strengthen our orchids, because weaker plants are usually the most prone to suffer all kinds of attacks of fungi or parasites. 

It is important that they receive adequate maintenance: change of pot, pot, irrigation , fertilizer, temperature and location, which corresponds at all times to the specific needs of each orchid. 

If you want to avoid orchid diseases through the appearance and spread of pests , you must be very careful and clean. Follow these tips and you will not regret it:

  • Eliminate the deteriorated or diseased parts of the plant at all times by trimming them and dispose them afterwards.
  • Heal the wounds with coal dust, which is a natural disinfectant.
  • Wash your hands thoroughly before and after proceeding to eliminate any diseased area, so as not to transmit diseases from one plant to another.
  • If you reutilize pots, this is fine, but you should clean them thoroughly with hot soapy water.
  • Of course, before proceeding to eliminate any part of the plant, you must disinfect the cutting tools well, such as scissors and knives.
Abnormal condition:Effects:Solutions:
Lack of lightFlowering does not occur. Flimsy stems, the plant loses vigor. Very dark green leaves.Search for a better location with indirect exposure to sunlight (through a blind or partially covered by larger plants avoinding direct sunlight).
If this is not possible, supplement with artificial grow lights (low pressure sodium lamps or similar lamps).
Lack of humidityThe lack of moisture can occur in the substrate and also in the air. If this happens, the leaves will wrinkle and lose vitality. 
The plant appears withered and the flowers stop its development. Roots of white color. It is possible that after a prolonged period of lack of water, some leaves turn yellow and fall.
Install a humidifier that sets a stable humidity level. Spray water more often, but if you install the humidifier it will suffice anyway.
Temperatures out of rangeExcess or defect of heat produces fall of the flowers and an arrest in the development of the floral wands.Correct by means of the appropriate elements the temperature mismatches. Change of location to indoors as normally there are more stable temperatures. Consider that there should be a clear difference in temperature between night and day.
Excess irrigationWhen there is excessive watering or water retention by poorly drained substrate, the roots often rot, acquiring a dark color and a weak texture. The leaves of the plant will progressively acquire a yellow coloration and, finally, the plant will die.Wait until the substrate is a dry between waterings. If the roots have begun to decompose, the best thing is a transplant with new substrate, eliminating (cutting) the diseased parts previously. It is also advisable to disinfect the pot or container of the plant.
Burns by the sunThe leaves burned by the sun usually take a yellow or dark brown color.Remove them from the current location. Cover the windows with a net or blind that filters the exposure to sunlight.
Excess of fertilizersIt can produce yellow spots on the surface of the leaves.Stop immediately the application of fertilizer at least temporarily. Water only with soft water.
Exposure to organic gasesOrchids are especially sensitive to organic gases (released by decaying fruits, animals or others) and that are not always perceptible to humans. The effects on the plant result in wilting and premature fall of the flowers.Orchids should be in a well ventilated environment and in which organic gases of any kind are not concentrated. Cambria orchids are hybrids more resistant to this exposure but nevertheless you have to be careful.
Presence of pollinating insectsThe pollinating insects are not in themselves a danger for the plant, nevertheless the pollination of the flower supposes its enclosure (once fertilized) and later fall. Therefore shortens the life of the flower.To keep the open flower as long as possible, we must avoid the presence of pollinating insects. To do this, take the necessary measures to prevent access. Conventional insecticides are not recommended as they can damage the plant.
Air currentsThey produce the premature fall of the flowers.While the orchid needs good ventilation, most species (except Vanda orchid) do not like drafts or continuous air streams. Therefore, it must be avoided that they reach the plants directly.

At A Glance: Signs And Symptoms of Orchid Diseases

  • Your orchid has become a large plant but without flowers or with few barbs. This is usually a sign of environmental problems. Check lighting, temperature, etc. We discuss this point below thoroughly.
  • Brown tips have appeared on the leaves of its orchid. This can be caused by several things. Excessive fertilization and fungal diseases are common causes of darkening of the leaves.
  • The leaves are very dark green . While dark green leaves are often a coveted feature of an indoor plant, if an orchid shows dark green leaves it means it is not receiving the right amount of light. Orchid leaves in good health are olive green.
  • The leaves of your orchid seem to be damaged by the sun; yellow, calloused, in the middle of the leaves . Orchids prefer indirect light. Exposure to direct sunlight for some time may cause damage to the leaves.
  • The leaves of your orchid have a wrinkled appearance. This is dehydration caused by an irrigation problem. The plant simply has not been provided with enough water or has been over-watered and the roots have rotted.
  • The roots have gone from being white / coarse / grayish green to being wrinkled . This is most likely an irrigation problem. If an orchid is not receiving the proper amount of water, the roots may begin to wrinkle.

Pests and Insects As A Cause of Orchid Diseases

Scale insects in the orchid (Coccoidea):

Parasites susceptible to attack our orchids are

  • The woodlice (they are usually distinguished by having a whitish cottony texture);
  • The mites (for example, the red spider) that tend to attack young buds, producing malformation in the leaves and the presence of small marks in the form of dots and tiny cottony threads;
  • the so-called leafminer insects that are specialized in creating small galleries inside the leaves, appearing on the outside of the leaf some marks as lines or cuts,
  • Small caterpillars) that directly eat the leaf and produce erosions, especially at the edges of the leaf. The most common way for your orchids to become infected with this insect is to buy an infested plant. Pillbugs are transmitted easily to healthy plants when they are next to an infected one and the caterpillars move from plant to plant. Colonization by caterpillars brought by air can also occur when the plants are outdoors. This can also happen indoors and in greenhouses, when the caterpillars float in the air currents produced by the fans. If you suspect the presence of mealybugs, isolate the infected plant immediately.
  • The cochineals are usually hidden on the underside of the leaves , they look like ovoid brown scabs. If the attack is important, it is possible to find woodlice on the flowers.  Normally the attack of cochineals occurs when the orchids are in a hot place and the environment is very dry. 
  • The lice of the wool. These are white insects, which look like small balls of wool. They are usually found on the underside of the leaves, and in the holes of the plant. For example, at the lower parts of the leaves.  The trigger for this plague to occur is environmental dryness. 
SCALE INSECTS (COCCOIDEA) ATTACKING A PLANT

Treating Orchids with Insecticides, eliminating scale insects:

From experience, the best to treat this type of pests that trigger orchid diseases are commercial insecticides. They are in any neighborhood store, they are cheap and their efficiency is very high. You do not need an insecticide for orchids, any one destined to the use in plants of the home and garden will serve you well. Always follow the label carefully and do not use a concentration different than suggested. Remember, insecticides can be harmful to people and pets.

Likewise, normally cleaning the area with a brush dipped in alcohol (ethanol) or a specific insecticide suitable for orchids with which we should treat the entire plant is sufficient.

Cochineals: They are removed with a soapy solution, spraying the affected areas . The scabs should not be removed, it is better to let them fall on their own.

Lice of the wool. For the lice of the wool, the solution is quite simple, and it is the same as in other similar cases: use a soapy solution with which we will clean all the leaves, eliminating lice from the wool.

Aphids In Orchids: Treatment

Aphids are small insects, their size can vary between 1 and 12 millimeters. Their colors can be green, black, brown or even translucent. There are 4,300 different species of aphids. Only 250 of these species cause problems in agriculture and gardening.

The worst feature to mention is that they are a common problem and the cause of numerous orchid diseases. The aphids feed by sucking the sap from the plants where they live.

In turn, they produce a sticky substance called molasses. Ants usually thrive with the honeydew and in some situations they even help to breed aphids, protecting them from predators. Another aspect of aphids that makes them difficult to fight is their ability to reproduce . 

Aphids can reproduce sexually or asexually and can give birth to nymphs or lay eggs. This happens several times a year and several generations can reproduce within the same year.

The pests include attacks and infestations by small insects that normally live on the plants and, therefore, create problems of various kinds.  The best known and common are the so-called aphids. Their development is very fast, as we mentioned above already, and they can create extensive colonies in a short time. In addition to the direct effects on the plant (stop growth, malformations, etc.) can transmit different types of orchid diseases. 

Aphids are the most common pest among garden plan and another important cause of orchid diseases. I refer to insects of green or black color, that we will find in the most tender buds of leaves or flowers. They are really dangerous because they can transmit diseases such as fungi or viruses from one specimen to another. 

They appear in dry and very hot environments. There are many home remedies, such as spraying with a combination of water, potassium soap and alcohol.  To treat orchid diseases originated by aphids, we can use this mixture on a cloth, cleaning the affected leaves and spraying the most delicate areas.

During the period of growth of the plant and coinciding with the arrival of a warmer weather, insects and pests can colonize our plants. Each one of them has peculiarities that need to be known in order to prevent their appearance first and eradicate them if they have already made an appearance in our plant.

APHIDS AND AN ANT ON THE LEAVES OF A PLANT (NOT AN ORCHID)

Symptoms Of Aphid Infection

You may know that your plant is infested with aphids when the leaves start to fall off. Aphids can be seen around the flower and the spike, especially where there is a bud, and at the bottom of the leaves.

Aphids are particularly harmful to all plants, not just the cause of orchid diseases. This happens because they feed on the sap of the plant, it stresses and prevents important compounds such as sugars and nutrients from reaching all the parts and growing well.

 The aphids carry with them harmful viruses that can be transferred and kill the plant. Finally, the molasses left by aphids is a perfect environment for the growth of harmful fungi, that we will also study below.

Remove Aphids From Orchids And Other Plants

You can easily remove the aphids from your orchid by simply directing a stream of water to the plant where the insects are present. If there are areas with a high concentration of aphids, you may consider pruning those parts of the plant.

The basic treatment for these orchid diseases derived from aphids, is with insecticides and acaricides. It is advisable to use acaricides based on neem extract since they are less aggressive to the orchid. Cinnamon powder can also be used in cases where the infestation is not very severe.

Insecticidal soaps are another pretty good option. The soap removes the outer layer of the aphid causing the aphid to die . Surely you will have to make several applications to make all the aphids disappear. However, be careful as too many applications in a row will damage the plant and any application can cause damage to the flowers. Soaps should not be used more than three times in a row, that is what I recommend.

You can use adhesive traps, these are yellow cards that prevent the spread of aphids from one plant to another. The aphids or aphids are naturally attracted by the yellow color and when they begin to colonize a new plant they will be first attracted by the traps.

Mites Causing Orchid Diseases

The mites that usually attack our orchids are difficult to detect visually. Because of this, we are not aware of their presence until the plant begins to give the first symptoms of the derived orchid diseases in the form of small spots and erosions on the leaves, and we can also notice a general decay of the plant, etc.

An easy way to detect mitesis is to pass a piece of kitchen paper or white cloth soaked in alcohol on the back of the leaf (bottom). Once past the white paper, if we see small gray spots, it is likely that these are insects. To make sure, we can also utilize a magnifying glass and check if those small gray spots move especially on the back of the leaf, in which case there would be no doubt. Another symptom is the presence of small fibrous threads that usually cluster in the form of whitish spots.

orchid diseases
IN THE IMAGE WE CAN SEE A LEAF WITH SMALL YELLOW SPOTS: IN THIS CASE, MITES (RED SPIDERS) HAVE BEEN DESTROYING THE PLANT FIBER FROM WHICH THEY FEED. THESE TINY INSECTS, ONLY VISIBLE BY MEANS OF MAGNIFYING GLASSES, ARE FOUND NORMALLY IN THE LOWER PART OF THE LEAF. THERE WE WILL NOTICE WHITE FIBERS IF WE OBSERVE CAREFULLY. 

Influence Of The Leafminer In Orchid Diseases

orchid diseases leaves

IN THIS PLANT; THAT IS NOT AN ORCHID, AS I DO NOT HAVE AN ORCHID ATTACKED BY LEAFMINERS TO SHOW YOU. YOU CAN SEE HOW LEAFMINERS AFFECT LEAVES.

Red Spiders Attacking Orchids

The red spiders hide on the underside of the leaves and are not easy to detect, many times we do not see them until they attack the upper part of the leaves, when orchid disease is very advanced and therefore it is easy to observe a spider web that covers the leaves. 

We can observe dots or spots on the leaves, and when you pass your finger along the leaf you will be stained with mites. 

They usually appear when the environment is very dry, as I indicated earlier above.

It is best to clean the plant well with a solution of water with potassium soap. It is also usually effective to spray the orchid with a solution of warm water with a few drops of milk. 

This treatment will be applied in the morning in the first hour, to avoid the appearance of fungi.

Bacterial Infections As A Cause Of Orchid Diseases

Bacterial Rot / Brown Rot – Pectobacterium – Diseased leaves of orchids:

Bacteria are pathogens that usually produce spots on the leaves or pseudobulbs with a common appearance of watery texture and darkening. The affected parts lose texture and die quickly by decomposition. 

Among the variety of orchid diseases, attacks by insects are not very frequent among indoor plants, unless they are in contact with other specimens that are outdoors during part of the year, and then are placed indoors. 

The sooner we detect the appearance of any kind of plague, the sooner and better we can act and the easier it will be to eliminate it and prevent orchid diseases from spreading to other specimens. 

It is important to perform a scrutiny in the plants regularly without forgetting the underside of the leaves , where usually the parasites remain hidden. 

It usually needs a lot of moisture to develop but once they have infested a plant they are usually lethal. The recommendation is to cut the affected part, isolate the plant and avoid watering for a certain time to prevent its proliferation. 

In some occasions the bacterial attack takes place in the neck of the plant by water retention. In these cases, the plant can die quickly when the entire axis or main stem decays. It must be ensured that there is no water retention at the base of the leaves.

Symptoms Of Bacterial Infections

Bacteria in their different forms can attack the orchids producing a rapid decomposition of the tissues of the leaves and other vital parts of the plant. However, they are the easiest to treat if we take some preventive measures on time.  So let´s see.

The clearest symptom of bacterial infection is that the leaves of the orchid turn yellow. Small patches of water soaked in the leaves that are often surrounded by yellow halos, as in the picture below.


LEAF ATTACKED BY BACTERIA. THE SYMPTOMS ARE THE TYPICAL WATERY TEXTURE WITH THE FORMATION OF A PATCH OF WATER IN THE AFFECTED AREA.
IN THIS CASE THE PROBLEM FOCUSED ON THE BASE OF THE LEAF, BUT COULD HAVE ATTACKED THE REST OF THE PLANT. I HAVE DISCARDED THE TWO LEAVES AFFECTED BY BACTERIA CUTTING THEM.

If nothing is done to treat the infection, it will quickly rot the leaves and roots. It spreads more slowly to rhizomes or pseudobulbs. Rotten leaves can have a foul odor and an appearance like wet.

  • Phalaenopsis orchids: The disease spreads very quickly and the plants can rot whole in 2 to 3 days. Bacteria are opportunistic organisms that can enter through wounds.
  • Dendrobium orchids: The leaves turn yellow and wet, then turn black.
  • Vanda orchids: The leaves develop translucent spots that turn black.
  • Paphiopedilum orchids: The leaves develop small round spots, usually near the middle of the leaf. The spots are initially yellow, but then turn reddish brown and pocha. The spot enlarges in all directions and can reach the crown of growth to end up reaching the end of the leaf. If left untreated, the disease spreads rapidly throughout the plant, eventually rotting the entire plant.
  • Grammatophyllum orchids: The leaves have brown spots soaked in water that turn black and pocha.
  • Cambria orchids: Leaves turn yellow, resembling symptoms of chlorosis. Cambria are more resistant hybrids, as I explain here. however, that resistance does not appear in my opinion in the cases of bacterial infections.

Orchid Diseases: Treatment of bacteria

Immediately remove infected tissue using a sterile instrument, spray bactericides containing quaternary ammonium products such as Physan or copper compounds on infected and adjacent plants following the instructions on the label (copper should not be used on dendrobuses or flowering plants).

Likewise, disinfect the culture area with a 10% bleach solution. Treat nearby plants, as well as those that are sick.

As a preventive measure we will quarantine the orchid attacked by bacteria, isolating it from the rest.

There is no effective chemical treatment, however, if we detect the problem in time we can try to disinfect the affected area with cinnamon powder. Cinnamon is a potent natural remedy with antifungal, antibacterial and insecticide properties, besides it has no side effects on the plant as it is a natural product.

After a successful treatment, obviously the affected area that suffered the death of the tissues will remain as a dark spot, but the plant continues to live and flourish normally.

Orchid Diseases Produced By Bacteria: Prevention

The disease spreads usually, in my experience, by spraying water, so avoid over-head irrigation if the disease is present. The pathogen favors in conditions of heat and humidity. If your plant becomes infected, keep the leaves dry, increase air circulation and reduce temperature and humidity (if possible). Periodic preventive aerosols with copper compounds help prevent infection, particularly during hot and humid weather (do not apply copper to Dendrobians). 

Black Rot In Orchids: Pythium and Phytophthora

Symptoms Of The Black Rot

Infections usually begin in the roots or in the basal portion of the pseudobulb, although all parts of the plant are prone to be affected. Orchid diseases spread quickly, and even more when the temperature and humidity are high.

Pseudobulbs, roots or rhizomes show purple-black infections, often clearly delineated and discolored in the center of the plant . The infection often begins at the roots and can extend up to the base of the pseudobulb or leaf. This causes the leaf to fall from the plant even with a slight shake.

The Cattleya orchid usually shows a creamy yellow discoloration on one or both sides of the pseudobulbs. The discoloration eventually turns black or brown and softens. The bulb rots.

CATTLEYA ATTACKED: LEAVES STARTED TO TURN YELLOW AND THEN TURNED BLACK. SYMPTOMS SHOULD NOT BE CONFUSED WITH THE SYMPTOMS OF CHLOROSIS, AS IN THE LATTER, THE LEAVES DO NOT TURN BLACK.

Black Rot Cases Treatment

Unless the plant is valuable, you will have to discard it, since the disease is highly contagious and will spread from plant to plant quite easily.

If instead, the plant is valuable, isolate it from other plants. Remove the infected tissue with a sterile tool, and soak it with a suitable fungicide. This procedure does not guarantee that the plant will recover.

Prevention of The Black Rot Disease In Orchids

The high humidity contributes to the spread of practically all orchid diseases. Avoid humid locations and measure the humidity frequently using a device for it.

Consider the use of a suitable fungicide such as Banrot, Subdue or Aliette, particularly during very wet periods.

Bulb, Stem, And Root Orchid Diseases

Fusarium Wilt In Orchids

Symptoms Of Fusarium Wilt

Fusarium blocks the flow of moisture through the vascular system of the plant.

  • In the Cattleya orchid: The Fusarium can infect the plant through the or invading the rhizome of plants that have been divided for reproduction. The pathogen often spreads due to inadequate hygiene. Generally as a result of the use of non-sterile cutting tools, which transfer the fungus from one plant to another.The infected leaves are yellow, thin, wrinkled or withered and eventually die. Severely infected plants can die in 3-9 weeks, while slightly infected plants slow their growth gradually by about a year. The diagnostic symptom in the Cattleya plant is a circle or band of purple or pink discoloration in the outer layers of the rhizome. It looks much better when the rhizome is cut. If the disease is extensive, the entire rhizome may turn purple and the discoloration may spread to the pseudobulbs.
  • Phalaenopsis and Paphiopedilums:   The infection can be caused by too high a salt concentration, low substrate temperatures and substrates that are too wet or contain too much peat. The roots begin to rot and the base of the plant rots later . The sunken spots on the leaves enlarge and form yellow veins, the old leaves become leathery and the younger leaves can turn reddish. The stem of the flower can develop sunken and rotten spots with a premature fall of the buds.
  • Cambrias: Personally, I did not have a case in my nursery, but doctrine considers that was is stated for Odontoglossums may apply too.

Treatment Of Fusarium Wilt In Orchids

In the Cattleyas, discard the infected part of the rhizome and the pseudobulb when you see a purple stripe.

After that, transplant only the part of the plant that does not show purple discoloration. Spray the plants after removing the infected parts with an adequate fungicide.

When a cutting tool comes in contact with a surface of infected tissue, it must be sterilized before performing a second cut.

In Phalaenopsis and Paphiopedilums, discard severely infected plants, remove the worst parts and all infected roots. Treat with a suitable fungicide.

FUSARIUM WILT ATTACKING THE STEM OF THE ORCHID

Prevention Of Fusarium Wilt

In Cattleyas, prevention is about following proper hygiene. In general, we can affirm that orchid diseases can be well prevented with hygiene and a correct setup of environmental conditions.

Sterilize the cutting tools after each use, preferably by flame sterilization. In the Phalaenopsis, adequate temperatures, correct substrate moisture and fertilization will help prevent its occurrence.

Fungal Rot: Rhizoctonia

Symptoms Of Rhizoctonia

Root rot occurs when the substrate decomposes, drainage is poor and / or the plants are too irrigated.

Rotting occurs when the roots are damaged by injury or salt accumulation due to hard water or excessive fertilization and the levels of the soilborne fungus Rhizoctonia solani increase to dangerous levels.

In the Cattleyas, the Rhizoctonia moves slowly from the older pseudobulbs to the younger ones. These turn brown and end up rotting. The roots of the oldest and most infected parts of the plant die.

Rhizoctonia, among all orchid diseases, is usually a disease of the roots, but the symptoms can be noticed in the aerial parts of the plant because nutrients will not reach them.

Therefore, it resembles the damage caused by Fusarium. The leaves turn yellow, wrinkled and finally fall off. The older pseudobulbs turn brown from bottom to top. So here we also notice different symptoms than in chlororsis.

RHIZOCTONIA IN AN ORCHID. SEE THE ROTTEN ROOTS. THIS IS A TYPICAL RHIZOCTONIA SYMPTOM

The fungi have attacked the roots first and caused their death. Progressively the leaves have turned yellow and falling when nutrients do not arrive. In this case there is no solution.

Treatment Of Rotten Roots In Orchids

Remove the infected part of the plant using a sterile cutting tool, soak the rest of the plant in a suitable fungicide. Disinfect the culture area with a 10% bleach solution.

Prevention Of Rhizoctonia

Make sure that the medium or substrate is ventilated and that your plants are not too watered. When the presence of the disease is suspected in other plants remove them, check their roots and replicate them as necessary. In hard water areas, the pots should be rinsed at least once every 3 months to avoid damage to the roots.

Fungi in Leaves And Flowers Of Orchids

Fungi are one of the main scourges of these plants, and one of the main causes of orchid diseases, however, it can be successfully fought if we detect the problem in time. 

In general, they manifest with dark spots or spots on the leaves and flowers. They can also do so by changing the color of the leaves to a shade that can vary from yellow to brown, black or gray, depending on conditions and type of plant. 

Fungi are one of the most common pests in greenhouse orchids, because they need a high humidity, along with high temperatures, ideal conditions for fungi to proliferate.

If you keep your orchids in an airy place, like a window sill, you will probably do not have problems with fungi.

You will know that your orchids have been attacked by fungi, if flowers with spots or brown parts in the leaves or pseudobulbs appear.

Normally an excess of moisture or water retention together with high temperatures and poor ventilation facilitate the appearance of fungi in its various forms. Generally speaking, these conditions will actually facilitate the appearance of orchid diseases. That is why we stress so much the point of the beginning of this article regarding

The best action is to control all these conditions and use a specific fungicide (there are some that we can recommend from Amazon) as a preventive action especially in spring. Orchids are very sensitive to any type of chemical treatment and some generic products could burn the leaves. 

There are many ways to prevent the appearance of fungi in orchids, the most practical is that where the orchids are installed, there is always a good air renewal. 


PHALAENOPSIS ORCHID WITH COLOR ALTERATION AT THE BASE OF THE LEAF: NORMALLY, WHEN THE LEAF BEGINS TO TURN YELLOW IN THIS AREA, IT IS USUALLY A SYMPTOM OF DISEASE.

WHEN THIS FEATURE OF TURNING YELLOW OCCURS IN THE OTHER END OF THE LEAF IT IS USUALLY NOT SERIOUS AND CAN CORRESPOND TO NATURAL DEATH. THESE PLANTS.

in their normal evolutionary course, ORCHIDS usually discard the oldest leaves to create new ones.

The most common cause is waterlogging or poor drainage in the POT containing the roots.

Pyllosticta Fungus

It spreads more easily in warm environments and with a high level of humidity. The genera most sensitive to this fungus are the Vanda, Oncidium, Cymbidium, Epidendrums and Cambrias especially. Some other horticulture specialists do not include Cambrias as sensitive to fungi as it is a stronger hybrid. However in my nursery I found that Cambrias are also sensitive to fungi and bacteria, the same as the Odontoglossums, from where this hybrid generally derives.

The first symptoms of these orchid diseases are manifested by small black or violet spots that later lengthen and give a very unpleasant appearance to the leaves of the plant.

The fungus reproduces by spores and it is convenient to eliminate the parts of the leaf or the whole leaf that is attacked. Some specialists, to avoid the propagation of the spores, advise to put some transparent nail polish on the affected part. The use of a specific fungicide will help you in the treatment.


DISEASE PRODUCED BY THE PYLLOSTICTA FUNGUS

Anthracnosis, Colletotrichum And Glomerella

Symptoms Of These Fungal Orchid Diseases

This fungal disease infects the aerial part of the plant. The leaves are attacked more frequently. The tips of the leaves turn brown starting at the apex and ending at the base. 

Dark brown or light gray spots develop, sometimes as concentric rings or as numerous dark bands along the leaf. The affected area is usually very defined and somewhat sunken, while the rest of the leaf seems normal.

The flowers develop watery, black or brown pustules that usually rise and are found in the lower part of the older sepals and petals. The spots can fuse and cover the entire flower.

The pathogen generally associated with anthracnose is Colletotrichum gloeosporioides (asexual stage, the sexual stage is known as Glomerella cingulata). Another pathogen is Colletotrichum theobromicola, not previously reported as a pathogen for orchids and therefore not identified as a cause of orchid diseases. This pathogen causes a chlorotic speckling on the upper surface of the leaf, with corresponding patches of small spots on the bottom of the leaf. There is an occasional sunken or necrotic spot.

ANTHRACNOSIS ON THE LEAVES OF A TREE.

Treatment Of Anthracnosis, Colletotrichum And Glomerella

Spray with a suitable fungicide that contains copper or quaternary ammonium compounds.

Prevention Of Anthracnosis, Colletotrichum And Glomerella

Normal hygiene, good air movement, lower temperatures (if possible) and an increase in light can help reduce the spread of this disease. The pathogen is more active in warm weather when light is low and humidity is high.

There are many ways to prevent the appearance of fungi in orchids, the most practical is that where the orchids are installed, there is always a good air renewal. 

Virus As A Cause Of Orchid Diseases

Viruses are also another common problem. Not the major cause of orchid diseases, but when it appears, it may absolutely kill your orchid.

Its attack produces a varied symptomatology. The most frequent symptoms are spots or dark / black spots on leaves. Normally, the affectation usually appears at the top of the leaf but can appear at any location. Other symptoms are: yellowing leaves (also a symptom for chlorosis so at this phase you still do not know which is the real condition), malformations in the leaves and flowers. There is no effective treatment.

THIS IS AN ATTACK BY THE MOSAIC VIRUS. CUT THE AFFECTED LEAVES AND DISPOSE THEM AS THERE IS NO EFFECTIVE TREATMENT.

Symptoms of Virus Attack In Orchids

More than 30 different viruses have been reported in orchids. Among them, the ring spot virus in the Odontoglossum and Cymbidium mosaic virus stands out, because they are the most widespread and serious due to the consequences they bring to the plant. 


Orchid plants are more likely to be infected by the virus. The symptoms that are caused by viruses are variable and difficult to identify. Sometimes, the infected plants are asymptomatic. 

The appearance of orchid diseases can be nevertheless suspected because the plants have a bad general appearance with lack of vigor (folded leaves, falls, etc.). Circular rings of yellow color may appear with irregular red or necrotic lesions of different sizes. 

SOME OF THE SYMPTOMS ARE STREAKS IN THE COLORS OF THE FLOWERS, AS IN THIS PICTURE. ALSO THERE ARE SHARP CUTS IN THE LEAVES OF THE FLOWERS.

Some of the symptoms of these orchid diseases are streaks in the colors of the flowers (this happened to me) or sharp cuts in the leaves of the flowers themselves.

The flowers may have a change in the original color, without other symptoms of chlorosis, as reported in my nursery.

Therefore, due to this great symptomatic variability, it is not easy to determine if the problem is caused by a virus or a combination of viruses and fungi since both can act together. 

Treatment of Virus Attacks In Orchids

There is no treatment for orchid diseases derived from virus attacks. Viruses are very difficult to eradicate in domestic conditions so if we suspect their presence, it is best to first cut the affected part, isolate the plant and if the symptoms remain, sacrifice it.

Viruses are transmitted by contact, it is advisable to be very careful when handling affected plants. A good idea is to use disposable gloves, even if they have increased their prices since 2020 until now, and if you have to make cuts, better do it without tools and always as we said, with the protection of these aforementioned disposable gloves.

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