Hungry caterpillars can turn healthy vegetable foliage into lacework in a matter of a few days. If allowed to continue their feeding frenzy, they can completely defoliate the plants or begin feeding on the fruit. Control methods include handpicking, destroying eggs and spraying with insecticides. No insecticide is completely harmless, but the two insecticides used to treat caterpillars, spinosad and Bacillus thuringiensis var. kurstanki (Btk), have little impact on the environment. Treat your plants for caterpillars as soon as you see them or the damage they cause. Insecticides used to kill caterpillars work best when the caterpillars are young.
Pick caterpillars off your crops by hand. Wear latex gloves or use tweezers if you don’t want to touch them. Drop the caterpillars on the ground and step on them or put them in a jar of soapy water to kill them.
Spray vegetable plants infested with caterpillars with spinosad. Mix the insecticide according to the label instructions and spray every four to seven days. Spray early in the morning or late in the evening to avoid killing honeybees. The spray remains active on the foliage for about five days. Once the caterpillar eats the toxin it may take up to two hours for it to die.
Apply Btk to the foliage, paying particular attention to the undersides of leaves. Btk is specific to caterpillars and will not harm beneficial insects; however, it will kill the larvae of any species of moth or butterfly that eats it. It may take several applications to get rid of the insects.
Check the undersides of leaves for masses of caterpillar eggs. Pinch off and destroy leaves with eggs on them. Use row covers to exclude moths from your vegetables.
Latex gloves or tweezers (optional)
Things You Will Need
Handpicking is the control method with the least impact on the environment. Children often love catching bugs. If you feel squeamish about picking up caterpillars, try enlisting their help.
Read insecticide labels completely and follow the label instructions carefully. Store all insecticides in their original container and out of the reach of children.