Garden Caterpillars

Tomato hornworm (Manduca quinquemaculata): Up to 4 inches long, bright green with white diagonal stripes and a black or red horn at the rear. Defoliates tomato, pepper, and eggplant plants rapidly. Look for dark frass pellets on leaves below feeding sites. If you find hornworms with white egg-like structures attached — those are braconid wasp pupae. Leave those hornworms in place — the wasps will kill them and provide biological control for future generations.

Imported cabbageworm (Pieris rapae): Small, pale green, velvety texture. The larvae of the small white butterfly seen in gardens. Feeds on brassicas — cabbage, broccoli, kale, Brussels sprouts. Leaves ragged holes and frass in the leaf heads. Check undersides of leaves for pale yellow eggs (single, upright).

Corn earworm (Helicoverpa zea): Enters corn ears through the silk and feeds downward. Also attacks tomatoes, peppers, and beans. Color varies — tan, brown, pink. Prevention is more effective than treatment for corn — mineral oil applied to fresh silk smothers eggs and young larvae.

Codling moth (Cydia pomonella): Pinkish-white larva inside apples, pears, and walnuts. Enters through the blossom end or side of fruit. Pheromone traps are valuable for monitoring adult emergence and timing preventive sprays.

Spinosad (Monterey Garden Insect Spray): Produced by soil bacteria fermentation, OMRI-certified organic. Highly effective against all caterpillar species. Works by contact and ingestion. Provides 5–7 day residual. Best choice for most home garden caterpillar situations — broader spectrum than Bt and slightly more forgiving of timing. Apply to both leaf surfaces at first sign of larvae.

Bt (Bacillus thuringiensis var. kurstaki): Bacteria that produces proteins lethal to caterpillar gut cells when ingested. Completely harmless to humans, pets, wildlife, and beneficial insects. Must be ingested by larvae to work — good coverage of leaf surfaces matters. Shorter residual than Spinosad (3–5 days). Best for heavy caterpillar pressure when targeted spraying is practical.

Manual removal: For hornworms and other large caterpillars in small gardens, hand-picking into a bucket of soapy water is highly effective and costs nothing. Early morning inspection when caterpillars are resting is most productive.

Row covers: Floating row covers over brassica crops prevent cabbage white butterflies from laying eggs. The most effective prevention for imported cabbageworm when properly installed before planting.