How to Kill Caterpillars on Tomato Plants

caterpillar image by Marek Kosmal from

Occasionally a pesky infestation of caterpillars appears on tomato plants, resulting in eaten leaves and stunted plant growth. While the lone caterpillar doesn't wreak enough damage to cause alarm, loss of too many leaves on a tomato plant stops development of new flowers and fruits. The plant must focus its energy on regrowing new stems with leaves. Hand-picking caterpillars and squishing them is an option, but when they hide and eat at night, it's a losing battle. Toxic pesticides kill all sorts of insect pests, as well as beneficial ones like honeybees and ladybirds. Luckily, one solution targets leaf-eating insects like caterpillars while sparing those that don't damage the plants.

Purchase spores or liquid bacteria culture of Bacillus thuringiensis (Bt). This organism, when applied to plant leaves, is consumed by leaf-eating insects like caterpillars, creates a hole in the stomach of the bug, causing it to die. Product trade names of Bt include Dipel (powder form) and Thuricide (liquid form).

Mix a solution of Bt with water in a spray bottle, according to product label directions.

Douse the tomato plant foliage with a spray of Bt solution, coating the leaf blade, stems and undersides--anywhere you see chewing damage from the caterpillars on the tomato plant.

Reapply the Bt spray once a week and after rain because the bacteria washes away. The caterpillars must consume foliage that has residue of Bt spray to be killed.

Most recent