What is Bacillus thuringiensis subspecies kurstaki (Btk)?
A Bacilus thuringiensis subspecies kurstaki, commonly referred to as Btk, is a rod-shaped bacterium that occurs naturally on dead or decaying matter in soil. It occurs naturally worldwide and is cultured specifically for pesticide use using high quality controls. Q How Does Btk Work? A Btk is only toxic to specific lepidopteran insects in the caterpillar stage of their life cycles. When Btk is ingested by the susceptible caterpillar, the highly alkaline environment of the caterpillar’s gut triggers the Btk bacterium to release a crystalline protein called an “endotoxin” that is toxic to the insect’s digestive system. The caterpillar must ingest the Btk bacterium in order for it to be effective. Btk does not affect adult moths and butterflies. Btk does not affect other insects, honeybees, fish, birds or mammals. There is also no impact on animals that may eat a Gypsy Moth caterpillar that has ingested Btk. Once applied, the Btk biodegrades quickly into the environment through exposure t
