How to Conquer the Most Common Chili Pepper Pests in the Greenhouse

There are a handful of insect pests that greenhouse chili pepper growers will likely run into during production. The good news is, there are also integrated pest management (IPM) best practices that growers can implement to prevent or even overcome an infestation.

The five most prolific insect pests on greenhouse chili peppers are thrips (typically onion or Western flower), aphids (green peach), leafminers, whiteflies (greenhouse and silverleaf), and psyllids (tomato and potato), and all five cause damage primarily by consuming and feeding on the leaves, stems, and other parts of the chili pepper plants.

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In this IPM guide, we’ll discuss how to identify each of these destructive pests and what treatment options, both preventative and curative, are available currently for greenhouse growers.

Thrips, specifically Western Flower Thrips (Frankliniella occidentalis) and Onion Thrips (Thrips tabaci)

Identification Tips: Thrips only feed on chili plants during two early lifecycle stages when they are larvae. They feed by slashing and slurping from the leaves or flowers. This can result in stippling (leaf areas with curling, rippling, and/or distorted growth) on the leaves, small-discolored spots, and/or silvering of the leaf surface. The later stages when they become adults are non-feeding stages that usually occur in the soil/planting medium. Immature thrips are oval shaped and do not have wings. Immature thrips are translucent white or yellow, while the adults tend to be darker yellow and tan to brown. Most adult thrips are long, thin, very small (less than 0.05 inch), and have long fringes on the margins of both long narrow wings.

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IPM Advice: Thrips can be difficult to control because most times, once damage is observed, the thrips may no longer be present. IPM techniques such as good cultural practices, use of natural enemies, and selective and/or least-toxic insecticides are usually able to control pest thrips populations. In some cases, predatory thrips, green lacewings, minute pirate bugs, mites, and some types of parasitic wasps can control pest thrips. After identifying the species of thrips in your greenhouse, you can select the predator of that particular species.

Aphids, specifically Green Peach Aphids (Myzus persicae)

Identification Tips: Look for soft, oval-shaped bodies with long legs, antennae, and a pair of tubes (cornicles) on the rear of the abdomen. Mouth parts are needle-like, making them suitable for piercing-sucking sap and potentially inoculating plants with viruses, such as the alfalfa mosaic virus. The commonly seen species are various shades of yellow to yellow-green to green. They feed on chili pepper plants by piercing the stems, leaves, and/or other parts of the plant and sucking the fluids. Low populations of aphids usually do not cause any damage, but larger populations can turn leaves yellow and stunt younger plants.

IPM Advice: Natural enemies are a favorable way of controlling aphid populations in a greenhouse. Parasitic wasps, lady beetles, lacewing larvae, soldier beetles, and syrphid fly larvae are all predators of aphids; some of these are available for release commercially. Contact insecticides such as insecticidal soaps and horticultural oils are usually able to sufficiently control aphids and can be used on organically certified chili peppers. The aphid infected chili pepper plants need to be sprayed thoroughly with insecticidal soap.

Leafminers (Liriomyza trifolii)

Identification Tips: Adults are small, shiny black flies with a yellow spot on their back (about 0.06 inch long) and red eyes. They are very wary and best seen on yellow sticky traps. The females puncture the leaves with their ovipositors (tubular organ through which female insects deposit eggs). The eggs that have been deposited into 1% of the punctures made by the female flies will hatch to produce a minute maggot/larvae that feeds in the uppermost tissues of the leaves, leaving a winding, light green blister-like trail only visible from above. The tunnels can also be black due to the maggot’s waste, or frass.

IPM Advice: When dealing with small infestations, infested leaves should be pruned and thrown away outside of the greenhouse. Preferably the leaves should be crushed so the adult leafminers do not emerge. This is a labor-intensive method and can also strip the plants of leaves that they need to grow. In larger, more extensive infestations, other control methods are necessary. Natural enemies are a suitable way of controlling leafminer populations. Parasitic wasps in the Diglyphus spp. may control leafminers. If necessary, an azadirachtin or Entrust formulation of spinosad can be sprayed in accordance with the product labels and can also be used on organically certified chili pepper plants.

Whiteflies, specifically Greenhouse Whitefly (Trialeurodes vaporariorum) and Silverleaf Whitefly (Bemisia tabaci)

Identification Tips: They are very small, yellowish insects about 0.06 inches with white wings. Greenhouse whitefly adults have wings that lay flatter over their backs, while silverleaf whitefly adults have wings that are slightly angled downwards. Whiteflies suck large quantities of sap out of the leaves and leave sticky honeydew all over the plant. Black sooty mold can grow over the honeydew, which is unsightly and can also reduce the amount of sunlight being absorbed by the leaves.

IPM Advice: Natural enemies are able to control whitefly populations in some cases. Whiteflies are parasitized by several minute wasps (Encarsia spp. and Eretmocerus spp.) that should be commercially available. Immature whiteflies are also attacked by bigeyed bugs, lacewing larvae, and lady beetle larvae. Contact insecticides such as insecticidal soaps or narrow range oils can be used to control whiteflies and can also be used on organically certified chile pepper plants. Infected plants must be sprayed thoroughly with insecticidal soaps or narrow range oils in accordance with the product label.

Psyllids, specifically Tomato (Potato) Psyllid (Bactericera cockerelli)

Identification Tips: The adult psyllid looks like a cicada and is very small (about 1/8 inch or 3 millimeters). The adults have white or yellowish markings on their bodies, colorless wings, and lines on the abdomen between segments. It is important to note the early growth stages of psyllids because as adults, they are fast moving and can be hard to see. Immature psyllids have a scale-like, flattened, oval, yellowish green to bodies with red eyes. Immature psyllids and possibly the adults, inject a toxin while feeding on the leaves. This toxin can cause transplants to die, but for larger plants in a vegetative growth stage it can cause stunting, chlorosis, curling of the leaves, and a yellowing of the leaves referred to as psyllid yellows. Psyllids also produce large amounts of honeydew, which often causes black sooty mold to grow and the fruit can potentially become unmarketable if the honeydew is not removed. It is important to note, psyllid honeydew dries as white powdery dots, unlike the liquid aphid honeydew.

IPM Advice: The natural enemies of psyllids attack too late in the psyllid life cycle to control psyllid populations; therefore, this is not a good management strategy. It is best to monitor the greenhouse with sticky traps near the tops of the growing plants and scouting the plants throughout the season for early detection. Entrust formulation of spinosad can be sprayed in accordance with the product label and can also be used on organically certified chile pepper plants to control psyllids.

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