Bt or Btk refers to a microorganism called Bacillus thuringiensis var. Bt has been widely adopted for gypsy moth control because of its efficacy, its low toxicity to other animals and its ease of use. This bulletin is designed to answer some frequently asked questions about Bt. . Bt is the abbreviation for Bacillus thuringiensis, a native bacterium that is commonly found in soil and on plants. Thousands of Bt strains exist in nature, each with its own unique characteristics.
Most Bt strains are insect pathogens that cause disease in specific groups of insects.
Though Bt products can be highly effective in controlling specific groups of insects, they have little impact on populations of other animals. Therefore, sprays made with Bt are much less harsh on the environment and on non- target organisms than conventional insecticides. The Bt products used to control gypsy moth during out- breaks are made from a single strain of Bt known as Bacillus thuringiensis var. This type of Bt specifically affects caterpillars. It has not been genetically modified.