Hornworm caterpillars (Manduca quinquemaculata), also referred to as tomato hornworms, can devastate tomato plant leaf and fruit in the summertime. Hornworm caterpillars are identified by eight V-shaped markings on their body and a notable horn in the rear. It’s imperative to eliminate a hornworm infestation whenever possible to stem the damage and protect against future infestations. There are numerous methods you can employ to get rid of caterpillars on your tomato plants, such as cultural, chemical, biological and physical.
Inspect your tomato crops two times a week in the summertime for signals of caterpillar infestation. Signs include unnatural defoliation, fruit hurt and small holes near the fruit stems. Look carefully for the caterpillars themselves, as they blend with the leaves.
Eliminate caterpillars from the plants by hand and destroy them by putting them in soapy water.
Till your lawn after each harvest with a tiller, working your way down the soil in rows. Till each row only once. Tilling eliminates burrowed caterpillars and caterpillar pupae.
Plant spearmint, clover or daisies in proximity to your tomato plants to attract paper wasps, a natural predator of the horned caterpillar. Paper wasps seldom have stingers and therefore are attracted to the insects. The small Braconid wasp also gravitates into the aforementioned plants. Braconids seldom have stingers and feed on the caterpillars until pupation and kill them prior to seeking other prey.
Apply insecticidal soap or an insecticide containing one of the following active ingredients: bacillus thuringiensis, permethrin, bifenthrin, carbaryl or spinosad. Follow the manufacturer’s instructions when using an insecticide regimen. Of the previously mentioned insecticides, bacillus thuringiensis kurstaki is naturally occurring and special to caterpillars.