House & garden

Orchid diseases – characteristics and tips to control

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As beautiful and easy to care for orchids as it is with all other plants, diseases or pests can occur for which correct control must be used. Since the orchids are mostly on the windowsill or in another sheltered place, they are very rarely attacked. Nevertheless, it is not uncommon for diseases to be introduced when purchasing plants, which can then be transmitted to other plants and orchids. Do you currently have problems with your orchids and suspect Orchid diseases, then we hope that we can help you with our list.

Orchid Diseases – Tips for Healthy Plants

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We have put together some common signs on leaves, as well as typical pests on the pretty orchids, with whose help you can fight orchid diseases. These tips can also be helpful for other types of plants. The pests in particular are not only common on orchids, but also occur on other specimens.

Orchid Diseases – Wrinkled Leaves

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This common problem is typical of the Oncidium, Miltonia, Cambria, Odontoglossum and Promenea, species that are more complicated to care for. The newly growing leaf of the plant appears wrinkled and is reminiscent of an accordion. If you have noticed such a problem, you will certainly be interested in what the reason for these orchid diseases is.

Orchids and diseases

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Like all other plants, these orchids have certain requirements in terms of their environment and care. Sufficient light, water and suitable humidity are important to avoid orchid diseases. If these are not offered, the plants will stop growing. If the plants feel good again, they will continue to grow. However, this creates these wrinkles. The bad news is that these wrinkles cannot be corrected afterwards. The leaves don’t look very pretty in the middle of the normal leaves, but luckily they don’t harm the plant. You can only avoid future accordion growth by taking care of species-appropriate care.

Orchids and Diseases – Falling Leaves

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Often with the Phalaenopsis variety, owners panic when leaves begin to turn yellow and, after a while, fall off. But this does not necessarily have to be related to orchid diseases. If the lower leaves fall off, this is usually a normal process. The fall of the older leaves is a normal aging process that usually takes place in the cooler seasons and in no way harms the plants.

Poor conditions

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However, you should consider the other options and check whether the conditions might not be inadequate after all. On the one hand, the reason for the loss of leaves can also be a lack of light. However, in this case, some or even all of the leaves will turn yellow. Now you should act quickly, because the weakened plant is now also more susceptible to orchid diseases. Put it in a bright place but out of direct sunlight.

Possible causes of illness


If there is nothing wrong with the location of your orchid, there are two other possible reasons for the yellow leaves. On the one hand it can be a pest infestation as an orchid disease (we have listed some pests below) and on the other hand a new substrate may be necessary. This should be changed every two years. Over time it disintegrates, condenses in this way and the roots, which require a lot of air, rot. This can be recognized by the yellow leaves.

Brown or black spots


Again, there are various possible causes for these orchid diseases. Sometimes the problem cannot be solved, which unfortunately can lead to the diseased plant having to be disposed of in order not to infect other specimens as well. But let’s not paint the devil on the wall right away. First, take a closer look at the stains to determine the possible cause.

Sunburn – a common problem in summer


As you already know, the direct sun doesn’t get the orchid good at all. The plant does particularly badly in a south-facing window if no sun protection is guaranteed there. When sunburned, brown spots appear that slowly turn black and, with prolonged exposure to the sun, can even turn white in the middle. You will also notice that it is a sunburn when the spots do not get bigger or spread and are dry. Now act quickly, because at an early stage (if the spots are more yellowish) they can even disappear again. Relocate the plant so that the weakened plant does not attract further orchid diseases. If you only have space in a sunny place, provide sun protection. Curtains, not completely closed blinds or even a larger, sun-loving plant are well suited for this.

Fungal infections


However, the spots are also brown in these orchid diseases, but they are not dry and spread slowly. The surface is uneven and some places have sunk. Fungi develop when there is too much moisture. So one reason is spraying the leaves with water too often. The so-called black spot disease (Phomopsis viticola) is contagious, which is why you should isolate the affected plant. Then cut off the affected areas. Use a sharp knife that must be disinfected beforehand and after each use. The same goes for your hands. Otherwise you risk infecting other plants. In addition to this, you can use an appropriate remedy. But that alone is often not enough, because mushrooms are stubborn. Also, reduce the humidity. You can ventilate for this purpose. But avoid drafts1

Bacteria as orchid diseases


Bacterial infections are just as persistent and highly contagious. Isolation of the diseased plant is therefore mandatory! In bacteria, the leaves not only turn yellow. These orchid diseases develop brown spots that are slightly sunken in the leaf and have a sharply delineated edge. In addition, there is often a damp surface on the leaves and mold. With such orchid diseases, disposal is usually the better decision, because healing is very difficult. However, if you don’t want to give up your orchid so quickly, proceed as with a fungal attack. Cut off diseased areas and do not forget about adequate disinfection. This also applies to the location of the plant. Use, for example, hydrogen peroxide. It is equally important that you change the substrate and the pot.

Rotting orchids – stem rot


The so-called stem rot is one of the typical orchid diseases. As the name suggests, it begins on the trunk and continues to spread to the leaves. This rot is caused by incorrect watering and bacteria in the water. It is important to note that the leaf axils, i.e. the area where the leaves grow from the trunk, must not be watered. The water stays there and cannot evaporate quickly enough, especially when the air humidity is high. That leads to the rottenness of the tribe. The same applies to excess water in the planter, which in turn affects the roots and the leaves, which turn brown in the area of ​​the axis and fall off after a while.

Watering properly to treat orchid diseases

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You should therefore water properly and make sure that you do not allow excess water to accumulate. If only a few roots are affected, the orchid can still be saved from these orchid diseases. All you have to do is cut off the rotten roots with disinfected scissors. After that, the orchid needs to be kept drier to get rid of excess moisture. However, if all the roots or even the trunk are rotten, it is rather impossible to save the plant.

Heart rot

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As mentioned, the starting point for rot as orchid diseases can also be in the area of ​​the leaf axils. You can save the plant as long as the bulb is not affected. In this case, cut off the leaves. The interface is then best disinfected with a charcoal powder. Cinnamon is also often used. Then water more sparingly and, above all, only by diving, so that water does not get back into the armpits and diseases do not develop in orchids.

Buds dry up and fall off – the cause is lack of moisture


These orchid diseases are quite common and can have various causes. The first logical cause is too infrequent watering. If the orchid dries out quickly, the buds are shed, but the flowers are also often affected. To avoid this problem, it is important that you keep a regular rhythm for watering. The best way to control this is to keep a specific day in the week for it. In summer, weekly watering is necessary, in winter it is enough to water every two weeks. The best way to control the rhythm is to choose a specific day and always stick to it. A look into the transparent pot is also helpful. Water droplets inside, as well as green roots, indicate that there is sufficient moisture. If the roots are silvery, it can be watered.

A change of location


When buying a new orchid, this is usually the cause and not some specific orchid disease. In your house, all the conditions are different than at the florist or hardware store. This switch stresses the plant, causing it to simply shed its buds. You shouldn’t be frightened by that. Because at the base of the former buds can form with proper care. If necessary, all you have to do is be patient until the new flower stem grows.



Some orchid diseases or problems are caused by drafts. This doesn’t do us humans very well either, how could it be otherwise with plants. But don’t let that put you off. The draft is not only caused by windows that are kept open too long. Even in winter when the window is closed, drafts can arise, namely when the orchid is on the window sill and over a radiator. The rising, warm air then creates drafts. The higher the ceiling, the greater the draft caused by heating air.

Dark location and direct sun


Orchids don’t like direct sun, but they need a lot of light. A north window is perfect in summer, but not enough in the rest of the year. This darker period of the year makes the plant shedding its flowers. Therefore, look for another permanent location or move the plant in good time. An east window or a location in the south or west with sun protection is perfect. Sun protection is particularly important to prevent orchid diseases, because not only the leaves can burn otherwise. The flowers may also be shed.

Pests on orchids


You are probably wondering how orchid diseases can come about when the pests are actually visible. That is not completely right. Many of the pests hide cleverly under the leaves or in the substrate and are only discovered when they have already caused damage to the plant. Regular inspection of the plant is the best prevention. If you have already discovered a change in the plant that cannot be traced back to the causes listed above, you are likely dealing with one of the following plagues. Isolate the infected plant to protect others and check the rest of the specimens as well as a precaution. You could already be infected.

Diseases due to mealybugs


Mealybugs belong to those pests that hide under the leaves and cause orchid diseases. They are also known as mealybugs. They can also be found in the leaf axils by building isolated nests. They damage the plant by sucking out the sap. You can recognize them visually by the fact that they are fluffy. Compare those with cotton swabs. While sucking the sap, they also secrete substances that damage the plant. This includes the fructose preferred by mushrooms. In the wild, beneficial insects such as ants or ladybugs help against the infestation. As a houseplant, however, you need help on your part. Soak cotton swabs in alcohol and remove the individual nests. Chemical agents rarely help because the mealybugs have a protective shell. A regular inspection is then necessary.

Orchid diseases – control scale insects


The scale insects as the cause of orchid diseases is very similar to the mealybugs. You are protected from chemicals by your shell and suck out the sap of the plant again. This is an advantage when using an agent that is first absorbed by the plant and then by the lice. However, it is a lengthy process. The quicker way to achieve success in controlling these pests is to use elephant or tea tree oil. Use a cotton swab to absorb the oil and then drip it onto the lice. The animals are isolated and no longer receive oxygen, whereupon they suffocate. This also acts against the brood at the same time. Simply scraping off the lice should be avoided. In doing so, you risk damaging the plant as well.



The hated aphids are rarely the cause of orchid diseases. However, if you have discovered some on your plants, it is probably on the young leaves, the flower stalks or the flowers themselves. There you suck out the juice again and, like the mealybugs, fructose. Again, since you can’t use the ants to help, use a chrysanthemum extract instead. It does not damage the plant, but works successfully against the annoying lice. After treating the orchid, check for more lice periodically.

Thrips in orchids


The thrips, which cause orchid diseases, receive the perfect living conditions through dry air. This is usually the case with a location above the heater. The winged and 1 mm large pests can usually be found under the leaves, where they pierce the cells in order to then suck up the sap. The leaves turn yellow and eventually fall off. Insecticides are very helpful with these animals. Alternatively, you can also prepare a solution of oil, detergent and water. Simply mix 2 tablespoons of oil and a little washing-up liquid with a liter of water in a spray bottle and spray your orchid. Repeat this several times until you are rid of the critters.

Spider mites


Like the thrips, the spider mites like dry indoor air. For this reason, increasing the level of humidity for a few days is very useful. For example, submerge your plant and then wrap the pot in a plastic bag. The tiny pests (0.3 to 0.5 mm in size) collect on the underside of the leaf. The spider mite bites, the cause of orchid diseases, discolor the leaves silvery, which again causes yellow leaves that later fall off. Insecticides won’t help you here. Helpers from nature are often used in greenhouses. The predatory mites prove to be the perfect fighter. It is done by hand in the apartment. Wipe the animals with a simple, damp cloth. Alternatively, spray the orchid with a solution of water and neem oil (neem oil), which you repeat several times.