Pine and Spruce Insects

Gypsy Moth

Gypsy moth (Lymantria dispar) feed on a wide range of plants including pines and spruces. When the hosts are present and the infestation is light, gypsy moth prefer 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, and trees in the Juglans genus. 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 is brownish and the adult female is whitish. The male can fly but the female in the midwest populations cannot.

The egg mass is about the size of a silver dollar and is light brown (tan). The eggs are laid whereever the female feels like leaving them (in car wheel wells, in side swing sets & gutters, sides of houses & trees, and so on). Eggs hatch in Northern Illinois about mid-May. The larvae climb from where the eggs were laid on 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 infestation 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.

Spray with Bacillus thuringiensis 'Kurstaki' (considered "organic") or check with your local land grant university (Cooperative) Extension Service for a recommended insecticide.

Written by James Schuster, Extension Educator, Horticulture, and reviewed by Dr. Phil Nixon Extension State Specialist, Entomology, University of Illinois at Urbana-Champaign.