Orchids' Insect Pests

Many insects and pests thrive on orchid plants. For instance, several large insects are capable of chewing the flowers and leaves of orchids. To get rid of such insects, you may use Carbaryl, Orthene or Diazinon.

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It is worth noting that scale insects suck out the sap from plants and it is necessary to deal with them as soon as you notice them because it may be difficult to get rid of them once they have established themselves in an orchid collection. However, spraying the plants with Diazinon or Malathion may help in controlling such pests.

Nevertheless, you need to undertake constant treatment of the plants over a prolonged period of time. You may also use mineral oil sprays available in the market for use on green-leafed plants. However, you need to use them after following the directions mentioned on their labels carefully.

Alternatively, you may swab the plants with methylated spirits or alcohol as it will give immediate results. Using a blend of vegetable cooking oil, a mild detergent and water in the ratio of 10 parts of oil to two parts of detergent to 1,000 parts of water is an effective home-made remedy that will also yield positive results in eliminating the pests from your orchids.

Put the oil and detergent along with a little water in a blender till the blend forms a white emulsion. Subsequently, add the remaining water. If you want to make this home-made remedy more effective, you may add Diazinon or Malathion at half full-strength. While spraying the blend, you should be cautious to cover the round-shaped female scales and also the disparate cotton-like male scales.

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Mealy bugs

Mealy bugs appear to be while owing to the cotton-like filaments surrounding them. These bugs are very sluggish and, similar to the scaly pests; they also suck the sap of orchids. However, different from the scaly insects, the exterior of mealy bugs is water-repellent.

These bugs have a propensity to conceal themselves inside the flowers and in crevices. However, all the treatments recommended for scaly insects above should also help to control these pests.

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Often aphids are found in large numbers inside the buds, flowers as well as the soft new growths even before you can notice them. However, it is easy to kill them using a wide variety of insecticides, which include Diazinon, Mavrik, and Malathion.

Alternatively, you may also use Orthene that has a contact as well as systemic actions. This pesticide is easily absorbed by the plant's sap stream and when the insects suck the sap, they get killed. In fact, aphids can be especially harmful for the plants as they are capable of harbouring plant viruses.


These are minute insects that move very fast and scrape the surface or the flowers and leaves. In addition, they are also sap-sucking. When the thrips move they leave behind silvery marks on the leaves.

You may eliminate these pests by using any of the sprays recommended for killing aphids. In addition to the plants, you should also examine the surface of the potting mix because some thrips species may also lie in wait there.

The two-spotted mite

For some orchids, especially cymbidiums, the two-spotted mite (scientific name Tetranychus urticae) is very harmful. This pest makes the underside of the leaves look silvery and makes it feel coarse like sandpaper. The color of the two-spotted mite may be reddish or straw-colored and its characteristic includes two black spots on its back.

These mites proliferate when the temperature is high and the humidity is low. They have a dislike for water. Spraying the plants twice in a space of 10 days using Kelthane or Pentac may be useful in getting rid of this pest. However, Kelthane will kill the pests but not their eggs.

Here is a word of caution – never use any of these pesticides in excess of thrice in 12 months because the two-spotted mite is infamous for developing resistant strains. In case it is absolutely necessary, you may change to any other chemical group, for instance Mavrik.

Aside from the two-spotted mice, a number of other mites may also damage your orchids. Some of these pests are so minute that you may require a magnifying glass to spot them. In case the insecticide sprays mentioned above do not prove to be effective enough to eliminate these mites, you may also use Diazinon or Malathion, which are more effectual.

Slugs and snails

It is necessary not to allow slugs and snails to enter the orchids' growing area. You may use baits that contain Metaldehyde or Mesurol to eliminate slugs and snails. In fact, a tiny snail is often found concealing itself in the pots and you will possibly not notice its presence until you remove the orchid from the pot.

This tiny snail bites off the root terminals and sides. It is difficult to kill this snail with ordinary baits as they are usually not effective against them. You may have to destroy such snails physically by shaking the potting mix from the orchids' roots.


If you see ants on your orchids or the pot, you should know that there is an infestation of aphids, scale or bugs. All these pests excrete sweet honeydew that lures ants. These ants serve as a guard to the insects. On their own, ants are not very harmful for orchids.

You can treat the presence of ants by getting rid of the honeydew. Ants are not very important in this case. You may deter ants by introducing diatomaceous earth in the pots. You can control fire ants, especially, using rotenone. In addition, introducing a beneficial predator called Pyemotes mites can also help as they ingest ant eggs.

Fungus gnats

Fungus gnats are very common. They are small flies that are generally a nuisance. More than the fungus gnats, their larvae is damaging for the orchids. The larvae are found inside the pots, especially in the organic potting mixes, where the gnats lay their eggs.

In addition, fungus gnats also cause fungal and bacterial root rots. As a result, the plants may start wilting, have root rots with maggots and their leaves may become deformed. Conditions like excessively wet potting mixes and too much shade promote fungus gnats.

They are introduced to the potting mixes via peat. You can treat the condition by ensuring that the potting mix is unharmed. First of all, you need to keep the growing are free from debris and lay down sticky traps straight along the pot's lip and another trap at the base of the pot.

Even using horticultural oils will help to kill the adult fungus gnats. You may use pot drenches of Bacillus thuringiensis (Bt) strain H-14 or insecticidal soap to eliminate the worms and their eggs.


Scales are tiny, round-shaped insects that move slowly when they are young. Subsequently, these insects attach themselves below the edges as well as midribs of sturdy leaves for survival. This insect sucks and sap out the juices from the plants.

There are several species of scales, but the basic types are only two. One type - the hard scales, have a brownish color and their body is coated with a defensive waxy shield below which they lay their eggs or give birth to offspring.

The other type - soft scale, may appear to be cottony masses of mealy bugs and they secrete muggy honeydew. The damages caused by scales to plants include yellow spotting. Often, scales also infest the roots of plants. Sometimes, the plants do not show any symptoms when infested by scales, but their vigorous growth is hindered.

You can treat scale infestation by cleaning your plants using a soft toothbrush. First dip the toothbrush in any soap or 70 percent isopropyl alcohol. You may also spray the plants with horticultural oil, insecticidal soap, swabs or alcohol. Here is a word of caution - never fertilize the plants in excess. In addition, lacewing is a accepted predator.


Though these pests are known as whiteflies, in reality they are not flies but a relation of scale and mealy bugs. Whiteflies also secrete honeydew. The adult whiteflies are white and waxy. They are capable of flying. The greenish nymphs are, however, more dangerous as their mouthparts can suck and feed heavily.

These nymphs attach themselves to the leaves' underside and lay eggs in a small circle. It is worth mentioning here that the activities of whiteflies are most when the environment is warm. The damages caused by these pests to your plants include drooping leaves along with sticky leaf residue or sooty mold.

They may even cause the leaves as well as the plants to die. You may treat the problem by vertically hanging yellow muggy traps a little above the plants. At the same time, reduce the amount of nitrogen fertilizer supplied to them. In addition, lower the temperature in the plants' growing area to reduce the activities of these pests.

You should also spray horticultural oil, insecticidal soap or pyrethrin on the plants to kill whiteflies. Encarsia formosa, a tiny parasitic wasp which is not harmful for humans, is a natural enemy of the whiteflies. In fact, Encarsia performs most excellently when the conditions are warm and humid.

Spider mites

Among all the pests that pose threat to orchids, perhaps the false spider mite and red spider mite are the most dangerous as they are also the most insidious. These pests are so miniscule that it is very difficult to see them and the first warning of their presence is the plants' leaves turning silvery in appearance, especially on their underside.

Subsequently, the color of the leaves changes to brown. It is often said that red spider mite is more prevalent when the conditions are dry. However, it is also capable of flourishing when the humidity level is high. During the winter months, when the duration of the day is less than 12 hours, red spider mites may conceal themselves in the greenhouse's frame and hibernate there in the webs.

Therefore, whenever it is possible, you should wash the frame of the greenhouse using watered down bleach during this time of the year to prevent the build-up of these pests.

However, the good news is that a predatory mite is there that provides an excellent means to control the spider mites biologically, Whenever you see that the numbers of red spider mites are increasing, you should introduce this predatory mite in the growing area of the plants.

This predatory mite is so effective that it equally attacks all the stages of the life cycle of red mite, including the eggs, nymphs and the adults. On the other hand, if you prefer controlling these pests using chemicals, you need to change the insecticide you use once in a couple of years because these mites gradually become resistant to chemicals.

In fact, the eggs of red mite are practically immune to all types of insecticides. Therefore, you need to use these chemical insecticides again after 10 days when they have hatched and nymphs have emerged. Apart from red spider mite, false spider mites are also very harmful for your orchids.

The false spider mites can also be eliminated with the same pesticides that you use to kill red spider mites. This pest is especially dangerous for pleiones. It conceals below the pseudo bulbs of this orchid and, in this way; it can get away from the pesticide.

You can deal with these pests by lifting the pleiones and spraying them with appropriate insecticides. You also need to use fresh compost as well as clean pots to be sure that the pests do not exist anymore.

Vine weevils

These days, the threat to orchids from vine weevils is on the rise. In fact, vine weevils destroy orchids in two ways. While the adult vine weevils eat the leaves leaving behind circular holes, the grubs, survive under the surface of the soil eat the roots and tubers.

The grubs are white pests with a brown head and measure about 8 mm (3/8 inch) in length. Though the damage caused by adult vine weevils may not prove to be fatal for the plants, but they make the plants look ugly and the effect of the damage lasts for a long time.

On the other hand, the grubs are more dangerous. It is unlikely that you will find the grubs, especially in a compound that is bark-based, and they may not certainly like rock wool. However, terrestrial orchids that are grown on peat-based compost are more at risk from the grubs.

Using the insecticide Sybol may help you to kill the grubs. You may also control the grubs using biologically. A parasitic nematode (a form of eel worm) is a natural enemy of vine weevils - both the larvae as well as adults.

The adult vine weevils are capable of entering the greenhouse via open vents and one of the ways to control them is using an insectocutor, which is an electrical device that kills insects.

However, the insectocutor will only kill flying insects that are drawn by the light of the device. Vine weevils are extremely mysterious pests and they only appear at night. If you enter a greenhouse after it is dark, you can trace the presence of wine weevils by following the sound of their crunching jaws.


Woodlice mostly feed on decomposed vegetable matter and many are of the view that they are not harmful for the living plants. But the fact is that woodlice definitely consume the emergent tips of the roots of orchids.

These pests lie in waiting under the pots that are placed on any solid surface. When you examine your pot, you may sometimes also find one inside the pot too.

Perhaps, woodlice do most harm to mounted orchids so that they are able to conceal themselves below the plant or behind a mount. Hence, it is always advisable that you examine the back of mounted plants occasionally. Fortunately, woodlice are susceptible to nearly all types of insecticides.

Garlic snails

These are tiny snails and have a flattened shell that measures roughly 5 mm (1/4 inch) across. Garlic snails are usually found in orchid houses and they move around growers on the plants as well as pots. These snails have a tendency to live inside the pot during the daytime and come out during the evening.

It appears slug pellets do not have any effect on garlic snails, but they can be controlled reasonably by talking a walk around your orchid house during the evening and crushing them physically whenever you notice one in the area. When these snails are crushed they emit a smell similar to that of garlic, hence they are named garlic snails.

Orchid growers in places having temperate climates are spared from predators like the giant African snail, which may be as long as 15 cm (6 inches) and are capable of destroying an orchid in a single day.


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