Gypsy moth feeds on a wide range of plants. When the hosts are present and the infestation is light, gypsy moth prefers to feed on alder, hawthorn, lindens, oaks (the most preferred tree), poplars and willows. As infestation is increased, black gum, elms, hickories, maples and sassafras are eaten. When infestations are at peak levels, the larvae also feed on arborvitae, beech, hemlock, pines and spruce. Larvae seldom if ever feed on ash, balsam fir, catalpa, dogwoods, holly, junipers, sycamores, tuliptree, walnut, and butternut.
Gypsy moth larvae eat tree leaves. Conifers are usually killed by one severe year of heavy feeding. Deciduous trees can usually tolerate several years of severe feeding before declining and possibly dying.
The adult male moth is brownish and the adult female mothis whitish. Both have black V marks on their wings. The male can fly but the female in the midwest populations cannot. The egg mass is about an inch long, one-half inch wide, and is light brown (tan). The eggs are laid whereever the female feels like leaving them (in car wheel wells, inside swing sets & gutters, on the sides of houses & trees, and so on). Eggs hatch in Northern Illinois about mid-May. The larvae climb from where the eggs were laid and spin a silk thread. Using the wind they may be carried several hundred feet to several miles. The larvae are covered with hairs that irritate many predators and sometimes humans may even develop irritations from the hairs. When infestations are light the larvae feed mostly at night. When infestations are heavy the larvae may feed continuously. After about 6 to 7 weeks, the larvae are ready to pupate. The larvae leave the trees to find a sheltered area. Adults begin to emerge in July. Usually the males are out several days before the females. Males can detect females as far as a mile away. The adults do not feed but die soon after mating and laying eggs
Control the caterpillars with sprays of Bacillus thuringiensis 'Kurstaki' (considered "organic") or other insecticides including insect growth regulators. Egg masses can be removed or killed with oil treatments (organic). Caterpillars and pupae can be collected from underneathburlap. Useone to two foot wide burlap strips tied around tree trunks. Fungal caterpillardiseasescan be spread by moving caterpillar cadavers from tree to tree.
This insect is effectively detected in new areas by the use of pheromone trapping conducted by government agencies.