Summit's Biological Caterpillar and Webworm Control is an all natural, organic Easy-to-Mix Liquid concentrate that kills only leaf eating caterpillars. The active ingredient is Bacillus thuringiensis subsp. kurstaki (BTK), a naturally occuring bacterium that specifically targets only leaf eating caterpillar pests of the insect order Lepidoptera. It effectively kills cabbage worm, tomato hornworm, tent caterpillar, fall webworm, Gypsy moth, and many more destructive caterpillar pests. In order to be effective, Caterpillar & Webworm control must be eaten by the caterpillar. The caterpillar soon stops feeding and dies within one to five days. The active ingredient (Btk) affects only the larval stage of susceptible insects; it cannot be used to kill eggs, pupae, or adults. Once inside the caterpillar’s stomach, where a basic (alkaline) pH is present, the bacterium releases a crystalline protein (endotoxin) that creates holes in the lining of the insect's gut. When the Btk is activated, the gut is paralyzed and the caterpillar stops feeding and dies within one to five days. Larvae are most susceptible to Btk when they are in the early developmental stages. This 100% natural alternative to synthetic insecticides is harmless to birds, earthworms, beneficial insects such as honeybees and ladybugs. It may be used on edible plants, fruits, and vegetables up to day of harvest and is OMRI® listed and approved for use in organic gardening.