Pest Problems

Orchids are relatively resistant to most pests, since the majority of leaf types are thick and/or tough. When pests do appear, they tend to target younger or tender parts of the plants, like emerging leaves or bloom spikes. Remember that sucking pests can spread viruses through your collection, so be vigilant in eliminating these problems.

Some pests can arrive on non-orchidaceous plants, like aphids, thrips or mealy-bugs. Others such as scale are very specific, and can only be introduced from an infested orchid plant.

Prevention is the best line of defense against pests. Acquire new plants from trusted sources, or isolate new arrivals for a minimum of 4 months to ensure they are clean, before integrating them into your collection.

Pest Name/Detail Type/Photo Description/Solution
Aphids Sucking insect
Size: up to 3 mm
Not specific to orchids. Can appear in different color forms, from green through reddish to nearly black. No difference in color types regarding damage or control. Tends to only target bloom spikes and buds, since these are the most tender parts of the plant. Easy to kill via most insecticides, or home remedies. They can spread on their own, or through species of ants.
Brown scale or orchid scale Sucking insect
Size: up to 2 mm
Leaves will often show some yellowed spots on the surface. If you check the underside of the leaf, there will be a brown hard bump. This is the female of the species, which creates a hard shell to protect itself. Fairly easy to eradicate by using insecticides or remedies that contain an oil of some sort, as this coats the shell and suffocates the pest underneath. Scale can survive on the root system for up to 6 months before surfacing, so repeated applications are necessary for eradication. If you're using a systemic insecticide like Orthene, then at least 3 applications at 2-week intervals is recommended. The males of the species appear as cottony masses, usually in the crook of the leaves, or around the base of the plant. These are often mistaken for mealy-bugs which are a different pest entirely.
Boisduval scale or white scale Sucking insect
Size: up to 2 mm
Leaves will often show some yellowed pitted spots on the surface. In the center of this area will be a flattened creamy-white spot. This is the female of the species, which creates a waxy shell to protect itself. Difficult to eradicate once it gets a good foothold. Try using insecticides or remedies that contain an oil of some sort, as this coats the shell and suffocates the pest underneath. Scale can survive on the root system for up to 6 months before surfacing, so repeated applications are necessary for eradication. If you're using a systemic insecticide like Orthene, then at least 4 applications at 2-week intervals is recommended. Particularly annoying also since the leaves remain damaged and pitted even after eradication. The males of the species appear as cottony masses, usually in the crook of the leaves, or around the base of the plant. These are often mistaken for mealy-bugs which are a different pest entirely.
Mealy-bugs Sucking insect
Size: up to 7 mm
Leaves will often show some discoloration, especially younger emerging leaves. Cottony masses will appear in the crown of the plant, and when brushed aside a fuzzy white insect appears with an elongated tail. Difficult to eradicate once it gets a good foothold. Try using insecticides or remedies that contain an oil of some sort, as this coats and suffocates the bug. Mealy-bugs can survive on the root system for up to 6 months before surfacing, so repeated applications are necessary for eradication. If you're using a systemic insecticide like Orthene, then at least 4 applications at 2-week intervals is recommended. It is also wise to repot the plant, disposing of the mix and sterilizing the pot, during the treatment period. This will reduce the chances of a re-appearance later on.
Slugs Feeding pest
Size: up to 100 mm


Slug damage on a leaf
Slugs come in several different varieties, depending on where you live. They prefer soft growth tissue to feed on, like emerging leaves or bloom spikes/buds. They are all susceptible to the same poisons, so treatment is the same for all of them. You can use any of the commercial slug baits to treat this problem. Manual removal is also an effective means of control. Be sure to monitor plants for the appearance of juveniles for a period of six months.
These pests are often introduced on plants that are summered outdoors. Be sure to inspect your plants well before bringing them back inside for the winter months. Presence of a shiny slime trail, is always evidence of this pest. Damage often appears as a layer of cells removed from leaf surfaces, leaving only the skeleton below.
Early damage on young leaves will appear much more pronounced when the leaves mature.
Bush snails Feeding pest
Size: up to 3 mm
Bush snails are tiny snails which reproduce quickly. They prefer soft growth tissue to feed on, like emerging leaves or bloom spikes. They are susceptible to the same poisons as slugs, and require the same treatment. You can use any of the commercial slug baits to treat this problem. Manual removal is also an effective means of control. Be sure to monitor plants for the appearance of juveniles for a period of six months. Presence of a narrow shiny slime trail, is always evidence of this pest. Damage often appears as a layer of cells removed from leaf surfaces, leaving only the skeleton below.
Thrips Sucking pest
Size: up to 1.5 mm


damaged leaf
Thrips are elongated slender pests, looking much like a tiny bit of fine wire and barely visible to the naked eye. They come in many colors, but green and black are the most common ones attacking orchids. They will live on many different types of plants, and usually target new growths and undeveloped flowers. This will lead to deformed flowers, because the feeding process deprives the buds of necessary sap. Thrips are unaffected by the usual insecticides. You need to use an insecticide that contains resmethrin, like Safer's Soap. Make sure this one ingredient appears on the label. This is a contact spray, and typically causes death of adults and juveniles within a couple of minutes. Repeat applications at 10-day intervals and up to four times to eliminate the problem. Thorough cleansing of the growing area is also needed, since they can live off of the plants for short periods of time, and adults are able to fly.
Centipedes Innocuous pest
Size: up to 60 mm
Although centipedes are not the prettiest insects around, they are totally harmless when it comes to your plants. In fact, centipedes are carnivores and may kill pests that are trying to attack your plants.
Millipedes Innocuous pest
Size: up to 60 mm
Millipedes are relatively harmless when it comes to your plants. They are attracted to decomposing plant matter, such as bark and rotted roots/flowers. Keeping a clean growing area and ensuring your potting mix is regularly refreshed will eliminate their food source. Rarely they have also been known to nibble on live roots, but that is usually when the potting mix is very degraded.
They vary from cream to beige when they have first molted their old shells. They move along fairly slowly, and will curl up into a spiral when disturbed.
Fungus Gnats Innocuous pest
Size: up to 4 mm
Fungus gnats are relatively harmless when it comes to your plants. Only the larval stage can do some minimal root damage, but typically requires very high numbers for that to be the case. This is another insect that is attracted to degraded potting medium, so keep it fresh would discourage them from showing up. Adults can fly.
Sowbugs or Pillbugs Innocuous pest
Size: up to 12 mm
Sowbugs are relatively harmless when it comes to your plants. They are attracted to decomposing plant matter, such as bark and rotted roots/flowers. Keeping a clean growing area and ensuring your potting mix is regularly refreshed will eliminate their food source. On occasion they have also been known to nibble on live roots or emerging leaves, but that is usually when the potting mix is very degraded or the population is large.
They vary in color from brown to gray, and will curl up into a little ball (like an armadillo) when disturbed.
White Flies Sucking insect
Size: up to 2 mm
Not specific to orchids. Prefers thin-leaved plants, since the juveniles feed on the sap. Hence, is fairly common in greenhouse environments and occurs on many types of house plants. Appear like tiny white moths. Fuchsia, lantana, geraniums (pelargoniums) are some of the common favorites. Tends to target the undersides of younger and more tender parts of the plant, and usually in groups. Easy to kill via most insecticides, or home remedies. They can spread on their own, and can fly.
True and False
Spider Mites
Sucking insect
Size: up to 1 mm

damaged leaf
True and false spider mites are not specific to orchids. They prefer thin-leaved plants, to feed on the sap. Hence, they are fairly common in greenhouse environments and also occur on many types of house plants. Barely visible to the naked eye. Feeding leads to a silvery sheen in damaged areas due to dried oozing sap. Fine webs may also be visible as evidence of true spider mites, and an absence of webs implies false spider mites. Tend to target the undersides of younger and more tender parts of the plant. Pitting of the upper leaf surface often results due to the damage. Prefer periods of lower humidity, so hot dry summers are the worst. They reproduce rapidly, and can cause much damage in a short period of time. Keeping the humidity up is often deterrent enough to keep the populations down. Although there are different species involved, treatment is the same. Easy to kill via most insecticides/miticides, or home remedies. They can live off the plants for extended periods of time, so repeated treatments and diligence are required.
Home-made Insecticides Remedies If very few pests are present, it is often sufficient to dab them with a cotton swab dipped in rubbing alcohol. This dries them out, and leads to death. However, if there are more present, or they are too small to see easily, you can spray with the following home-made mixture with good results :
  • 9/10 quart of warm water
  • 1/10 quart of rubbing alcohol
  • 1 tsp of lightweight oil (Neem Oil is an excellent choice)
  • a few drops of gentle dishwashing detergent
    Put into a spray bottle, and agitate vigorously. Then spray all plant surfaces, ensuring coverage both under and above leaves. Agitate the bottle frequently between uses, to keep the mixture suspended. Keep the sprayed plant out of bright light, as the oil will trap heat and may damage the plant further. Repeat at least 4 times, at 2-week intervals. After spraying regimen is done, monitor plants closely for a few months to ensure the pests do not reappear.
  • Start over Click Here I didn't find my answer, so I want to start over again.
    You can also use the browser "<- Back" button to navigate through the diagnosis.