Safer's BTK Biological InsecticideSafers BTK caterpillar killer is a biological insecticide that controls caterpillars including cabbage worm, tomato hornworm, tent caterpillars, gypsy moth, leafrollers, and other listed insects. Simply mix the concentrate with water and spray on vegetables, fruit, trees, and ornamentals. After ingesting the treated portion of the leaf, caterpillars stop feeding within hours and die within a few days. 100mL concentrate makes 33. 3L of solution.