Orchid parasites are an issue that can set a threat to your orchid species, especially if you are cultivating them for ornamental purposes. This is why as gardeners, it is important to maintain ideal growing conditions to help your orchids fight these parasites, thereby limiting the damage they can do.
But sometimes, no matter how conducive the growing environment is, these parasites still work their way into your orchids, and if you don’t know the proper steps to take, they can kill them in no time. Let’s look at different types of orchid parasites, their effects, and what you can do to control them.
Contents
What Are Orchid Parasites?
Orchid parasites are pests that depend on orchids for their growth and survival. They are often small and go unnoticed, damaging the plant through its flowers, leaves, and stems. However, these parasites can be controlled or prevented to avoid the reduction of orchid populations in cultivation and the wild.
What Are The Different Types of Orchid Parasites?
The different types of orchid parasites are fungal, bacterial, viral, or insect. These parasites infect their host plants in various ways and can pose a significant threat if unnoticed. However, unlike fungal or bacterial parasites that can attack any species, insects are more specific and only target certain orchid species.
– Fungal Parasites
Fungal parasites on orchids are pathogens that enter through the orchid’s roots, leaves, stems, and flowers. If control mechanisms are not employed once the symptoms they leave show, these parasites can quickly lead to the plant’s death.
These fungi develop when the growing conditions around the orchid are moist and humid or when an infected tool is used on the orchid. They would start causing various symptoms such as bud drops, leaf discolorations, white, fuzzy growth on the leaves, stems, or flowers, wilting or drooping of leaves, root rot, and stunted growth.
Some common orchid fungal parasites include Fusarium, Phytophthora, Pythium, and Rhizoctonia. These fungi are often introduced through contaminated water, soil, or plants, and with their simple contamination, if they find the area suitable, they will grow and have greater growth.
However, they might only attack the plant once the conditions are conducive. Hence, these fungi begin to attack when your orchids are left to sit in water due to overwatering, poor drainage, or high humidity levels without enough air movement.
– Insect
Most insect parasites attack orchids by feeding on their tissues and sucking their liquid nutrients, causing severe damage in large infestations. These insects include scales, spider mites, thrips, aphids, whiteflies, and mealybugs; as they are inconspicuous and can easily go unnoticed, especially at the early stages of their infestation.
However, once they begin to feed, they reproduce quickly, and small infestations can quickly become large. At this point, you will notice many ants on your orchid’s leaves due to a sweet, sticky residue on the leaf surfaces known as honeydew. For instance, honeydew is the by-product of the insect’s feeding and can also promote the growth of a fungus known as sooty mold on the leaves.
You would also notice small, brown spots on your leaves, slivering on their undersides, deformed flowers, and flower buds, yellowing, dropping, and curling of leaves, and a decline in the plant’s overall health. With spider mites, however, there will be small silk webs on the leaf’s undersides.
Orchid insect parasites are not limited to these sap-sucking pests that would damage the plant in the longer run. Insects such as the Euploea tulliolus butterfly are known for laying their eggs on the leaves of some orchid species, while the orchid weevil feeds on their flowers.
– Bacterial Parasites
Bacterial parasites enter orchids through their leaves, stems, and roots and can also cause serious damage to the plant if not detected and controlled immediately. Like other parasites, they are introduced when conditions around the orchids are less than conducive, such as excess moisture, inadequate ventilation, temperature fluctuations, overcrowding, or injury to the plant.
Using contaminated gardening tools without washing and sterilizing them first can promote bacterial infections. Moreover, you must also know about the common bacterial pathogens that can attack orchids, including Erwinia, Acidovorax, Pseudomonas, and Xanthomonas.
Once infected, orchids develop symptoms like soft, slimy, smelly rot or black, water-soaked lesions on the leaves and stem. They can also cause brown or yellow leaf spots, which can enlarge, cause the leaves to wilt, or lead to stunted growth, eventually killing the plant.
– Viral Parasites
Viral parasites invade the cells of orchids and quickly multiply within them, causing distortion, streaking, yellowing, and stunting of leaves and flowers. Close to 30 viruses, such as the mosaic virus, are known to affect orchids worldwide, and how they impact the physical structure of the plant.
These viruses are not only common for their prevalence worldwide but because of the severity of their symptoms and the fact that they are often transmitted together. Their symptoms can range from mosaic patterns on leaves, downward leaf curling, yellow or red necrotic lesions, purple blotches on leaves, and yellow, circular rings on leaves, to stunted growth and distortion of flowers.
However, symptoms only start to appear after six weeks of infection. And they appear as small, chlorotic patches. Other common viruses include the Cattleya mosaic virus and the Tobacco streak virus; they are often caused by using contaminated tools for propagation and pruning. Infected plants can also transmit them or transfer sap by insect vectors.
How To Control Parasites in Orchids?
To control parasites in orchids you can use chemical control methods such as targeting with the right oil, or you can try to prune the damage or repot the plant. Lastly, you may also try using biological methods, such as placing predator pests.
– Chemical Control
Using chemical sprays and oils is one of the most effective ways to eliminate parasites on your orchids. However, with this method, you must be careful when applying the chemicals, as some might be too harsh and cause further damage to the plants. So, it is best to test the chemical on a small part of the plant before application.
For insect parasites, you can use insecticides created for use on orchids if the infestation is significant. You can confirm their safety from your local gardening store. Neem oil or when you choose to use insecticidal soaps are both also effective solutions to large infestations. If you detect the insects at the early stages of infestation, you can also use alcohol solution spray, a mixture of isopropyl alcohol mixed with water.
The best way to avoid parasites on your orchids is to prevent them by maintaining proper growing conditions, especially since viral, fungal, and bacterial infections can’t be cured unless you use fungicides. The latter is a method that can be used to treat the orchids, while bactericides can be used for bacterial parasites.
– Pruning and Repotting
Pruning and repotting are important to remove diseased and decayed parts of your orchids. You can prune away yellowing or wilted leaves, diseased flowers, rotten roots, decayed stems, etc. When pruning, it is crucial to sterilize your tools before use. This is especially true if your plants have a viral, bacterial, or fungal infection to avoid infecting them further.
Sterilizing can be done using rubbing alcohol or a household disinfectant. Some gardeners also sterilize by dipping their tools in ethanol or bleach. You can also pass it through fire for a few seconds to kill potential pathogens.
Repotting should be carried out when the roots have been affected by the disease, as with the fungi that cause root rot, and this would be a method to free from them. In such a case, you would have to remove the plant from its growing medium, prune away the affected roots, and then spray with a fungicide before repotting in a new pot with fresh potting mix.
– Biological Methods
Using biological methods would work best for insect parasites and involves introducing some of their natural predators to feed on them and the younger ones. This approach may only partially eliminate the pests but will drastically reduce their population. So, it is best to use it when the infestation is still small.
If you are growing your orchids in a greenhouse or outdoors, you can introduce lacewings, Phytoseiulus persimilis, or lady beetles. Before purchasing these natural predators, research the natural enemies of the specific pest you want to eliminate.
Are Orchids Parasitic or Symbiotic Plants?
Orchids are not parasitic plants, but some species are symbiotic. Some orchids are epiphytes, which is where the misconception of them being parasitic originated. They grow on trees and other plants but do not obtain nutrients from them, getting nutrients from the air, water, and other organic matter around them.
However, some orchid species form a full or partial symbiotic relationship with fungi. Such orchids are called mycoheterotrophic because they obtain nutrients, like carbohydrates, from mycorrhizal fungi rather than photosynthesis. Plants give fungi food and water from their roots and seeds, and this relationship is most common among young orchids.
Some orchid species are saprophytic, meaning they get their nutrients from decaying or dead organic matter instead of through photosynthesis. These orchids usually tend to be small and yellowish due to a lack of chlorophyll, and you will see them looking weak.
Some of these orchids might grow below the soil and thrive entirely underground. In truth, most orchid species, particularly terrestrial orchids, pass through a saprophytic stage when they are seedlings.
– Corallorhiza
Corallorhiza, also known as coral root orchids due to their coral-shaped rhizomes, are a genus of up to 11 species occurring throughout North and Central America. Many of its species have no roots or leaves and produce little to no chlorophyll because they don’t photosynthesize.
Their stems can be reddish, purplish, brown, or yellow, but some species can photosynthesize to an extent and have greenish stems.
Depending on their location, these orchids are hardy terrestrials and bloom in spring, summer, or fall. They bloom with up to 40 flowers, which are showy but inconspicuous and come in colors from yellow, reddish brown, and white. On the other hand, the mature coral root orchids disappear underground about a year after flowering and remain there for several years before reemerging.
– Epipogium
Epipogiums are a genus of three terrestrial, perennial herbaceous species with fleshy underground rhizomes and self-pollinating flowers that are the only part above the soil. These orchids occur in rainforests as they would be ones that are leafless without roots. They bloom in summer or spring with short-lived, tubular flowers in yellow, cream, or pink colors with violet or reddish-brown marks.
– Gastrodia
Like epipogiums, gastrodias are also terrestrial perennial herbs with about 90 species in their genus. These leafless orchids derived their name from their flowers.
They also have fleshy stems and bloom in spring with few or many brown, bell, or irregular tube-shaped flowers that only live for a month. These orchids are the only species that bloom with cleistogamous flowers, meaning they don’t open when they emerge.
Conclusion
If you have orchids, you must do everything possible to prevent parasites from infesting and killing them. Here’s a quick recap of some of the major points you should note:
- Always ensure the area around your plants and the tools used on them are sterile.
- There is no such thing as parasitic orchids; some orchid species are symbiotic or saprophytic.
- When using the chemical method, test a small spot of your orchid’s leaves before applying it to avoid damaging the plant.
It isn’t a fun experience when parasites take over and threaten the health of your orchids. With the information in this article, you should be able to identify and successfully control different parasites on your plants.
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