Bt does not harm people, animals, birds or fish. Sprays also don t affect gypsy moth caterpillars outside the treated area. Sometimes spray programs are repeated for one to three years when the gypsy moth population is in the outbreak stage. Once the gypsy moth caterpillar population has collapsed in an area, spraying can stop for several years. The rapid migration west of the gypsy moth in the United States is caused by people unknowingly moving egg masses that are attached to cars, firewood, nursery plants and outdoor furniture.
Wind can move male moths and young caterpillars, but it doesn t spread the moths rapidly.
There are regulations requiring the inspection of logs, nursery plants, Christmas trees and outdoor household items which help reduce the number of accidental introductions, but it won t stop them all. We must teach people about these invaders and have them check the trees in their community. Check your patio furniture, trees and sheltered spots on buildings for egg masses in the fall. Give permission to state and federal trappers to place and monitor gypsy moth traps on your property. Learn more about the gypsy moth in Wisconsin.