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Health Facts
Control Agent

Only one gypsy moth control agent is used in the state suppression program, a biological insecticide called B.t. or B.t.k.. B.t. is an abbreviation for Bacillus thuringiensis var kurstaki which is a soil bacterium which produces a protein which binds to specific receptors found only in the guts of Lepidoptera (butterflies and moths) and eventually ruptures the gut walls, causing septicemia and death.

The Pennsylvania Department of Conservation and Natural Resources (DCNR) states that "B.t. has the highest known degree of safety to human health and the environment of any insecticide currently on the Market." The US Department of Agriculture (USDA) has published extensive information on B.t. in their Gypsy Moth Environmental Impact Statement (EIS) which is available in a book (but not in PDF) format from the USDA. The USDA concluded that based on "both the available epidemiological studies as well as a long history of use, no hazard has been identified for members of the general public exposed to B.t.k. formulations".

The USDA ranks relative risks to the public in all their activities by an index called the Hazard Quotient (HQ). The HQ is measured on a logarithmic scale, from 0.0001 to 10,000. A value greater than 1 means an effect may be observed after exposure. B.t. is given a value of 1 (2 in cases of extreme exposure). By contrast, an infestation of gypsy moth is given an HQ of 100, with an extreme exposure being given an HQ of 7,000. This is a result of skin lesions, respiratory tract effects as well as the psychological stress associated with living with large numbers of caterpillars in a homeowner's vicinity.