Centre County Government

Gypsy Moth Program

Health Facts

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.

A summary of the EIS (which only has two paragraphs on B.t.) is available here.

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If you have any anxieties about B.t. spraying, we encourage you to call the Gypsy Moth Coordinator in Centre County to discuss your situation. If after discussion with the county and reading the available materials about the safety of B.t. spraying you want to opt out of the spray program, please download the Objector to Spraying - Option Selection Form [PDF], fill it out and return it to the county office by the end of the year.

Objectors have two options; either to elect not have their property sprayed, or, to avoid any drift being deposited in their property, to effect a 500 ft wide no-spray boundary around their property. Objectors should keep in mind that such a boundary will usually affect their neighbors who may want to get their property treated.

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Although B.t. is the only approved insecticide for state suppression projects which use federal money, you may come across other insecticides used in private suppression programs. You may have also heard of Gypchek, which is produced by the Untied States Department of Agriculture (USDA) Forest Service for use in ecologically sensitive areas.

A comprehensive data sheet on B.t. is available as a pdf file from the National Pesticide Telecommunications Network here [PDF].

The USDA Forest Service produces enough Gypchek to treat 14,000 acres per year. The material is used in federal and state gypsy moth control projects where there are sensitive lepidopteran species (butterflies and moths) in the treated areas which could be killed by B.t. Gypchek contains NPV virus particles from gypsy moth and is made from infected larvae. A one-page data sheet on Gypchek is available here [PDF].

Insect Growth Regulators are used in gypsy moth suppression programs. One that has been used for many years is Dimilin (diflubenzuron). A data sheet on Dimilin is available here [PDF].

A more recent compound. Confirm (Tebufenozide) is proving to be very effective against gypsy moths. Here [PDF] is some more information on it.

Click on the insecticide links to open the pesticide labels for each insecticide.