a newly found gypsy moth colony. Pesticides The decision to use pesticides is influenced by a number of factors, such as the quantity of visible egg masses, The percentage of preferred hosts, presence of dead or dying branches, and proximity to heavily infested woodlands. When numbers of gypsy moth larvae are high, pesticides may be the most effective method of killing larvae. Available pesticides fall into two groups: microbial or biological and chemical (table 1). Microbial and biological pesticides contain living organisms that must be consumed by the pest. These include bacteria, viruses, and other organisms; biologicals include man-made synthetics of naturally occurring organisms. These pesticides are applied before the larvae reach the third stage of development. As they mature, larvae develop resistance to microbial pesticides. Low dose pheromone systems are used in Jersey, Channel Islands, to flood areas with synthetic pheromone and effectively 'blind' males so they are unable to locate females. Nucleopolyhedrovirus (NPV), a naturally occurring organism, has been developed as a microbial pesticide. It is presently registered under the name Gypchek and is available for use in USDA Forest Service sponsored suppression programs. NPV and Gypcheck are specific to the gypsy moth. Bacillus thuringiensis (Bt) is microbial and biological. It is the most commonly used pesticide and is used against other pests, including the western spruce budworm and other Choristoneura and the tent caterpillar. When Bt is taken internally, the insect is paralyzed, stops feeding, and dies of starvation or disease. Chemical pesticides are contact poisons and stomach poisons. The timing of application is less critical than that of microbials and biologicals. Chemical pesticides can affect non-target organisms and may be hazardous to human health. The most commonly used chemical pesticides currently registered by the US Environmental Protection Agency (EPA) for use against the gypsy moth contain carbaryl, diflubenzuron, or acephate. Malathion, methoxychlor, phosmet, trichlorfon, and synthetic pyrethroids (permethrin) are registered by EPA but are used infrequently. Several studies by Peter G. Kevan et al of the University of Guelph conducted between 1975 and 1995 showed serious reduction in pollination of blueberry and other crops due to aerial applications of insecticides that killed non-target wild bees. Diflubenzuron is an insect growth regulator and interferes with the normal molting process of the larvae but does not affect adult insects. Aquatic crustaceans and immature, non-target insects that undergo stages of molting are often sensitive to this pesticide. Mating disruption