Large caterpillars are abundant, and may wander in search of cool, shady areas, often resting on the sides of houses and trees during the day. In addition, caterpillar droppings, known as frass, rain down on driveways and picnic tables. Some people experience skin or eye rashes or respiratory allergies when they are exposed to the hairs on the caterpillars. Most gypsy moth outbreaks typically last two to four years in urban areas, then collapse, usually because the caterpillars die from viral and fungal diseases. Parasites, predators, starvation and unfavorable weather may also help reduce gypsy moth numbers.
Populations remain low for a few years until some unknown factors trigger the next out- break.
Though the gypsy moth will never go away, you have a variety of options to help manage this pest during outbreaks. One option involves the use of Bt to protect tree foliage and reduce the annoyance caused by gypsy moth caterpillars during an out- break. 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. .