How to Kill Grubs in Orchids

Destroy plants infested with orchid flies to eliminate the grubs. The flies seek orchids that have a pseudobulb, a water storage area originating from the stem. They lay their eggs inside, where the larvae proceed to feed on the plant. Burn host orchids if that is feasible. If not, seal them in a trash bag and throw it out.

Prune and discard root tip galls caused by cattleya midges. If your orchid fails to thrive for no visible reason, gently take it out of the pot. Look for yellow maggots on the roots and any galls. Trim the root system to get rid of them. Repot the plant in a fresh batch of orchid potting mix.

Spray permethrin insecticide on indoor orchids infested with adult cattleya weevils to prevent the larvae. Use the same product or another containing the chemical methoxychlor if the plant is outdoors. Apply either pesticide according to the manufacturer's label. The adult beetle is about 1/2 inch long with white markings on its back.

Trim and discard orchid pseudobulbs hosting the dendrobium borer. The insect is very small and brown. You might not see its larvae, as they bore tunnels inside the plant to feed, staying out of eyesight.