Organic farmers and home gardeners have been using Bacillus thuringiensis, referred to as Bt, for decades to manage pests in the garden. This naturally occurring microbe found in the soil, produces proteins that are toxic to the larva of certain insects.
Bt is sold as a powder, granular, dust or pellet. When the susceptible insect eats it, the toxins become active, the insect stops eating and dies within hours or weeks.
Different strains of this microbe affect different insects. Kurstaki often sold as Dipel or Thuricide kills true caterpillars, the immature stage of moths and butterflies. Use Bt israelensis found in Mosquito Dunks and Bits to kill mosquito and fungus gnat larva.
As always read and follow label directions carefully when using any product.
A bit more information: Research shows Bt does not harm people or non-susceptible insects when ingested. Avoid harm to beneficial moths and butterflies with proper timing. Apply it at the proper time and only to plants being damaged by caterpillar pests such as cabbage worms.
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