August 1996
Lepidoptera: Lasiocampidae, Malacosoma americanum
PLANTS ATTACKED: Black cherry, choke cherry and apple are favored; also feeds on hawthorn, pear, plum, and flowering fruits.
DESCRIPTION OF DAMAGE: Defoliator. The larvae initiate small webs in branch crotches as soon as eggs hatch. As the larvae feed on the foliage, they continually increase the size of the web until it is a large nest or tent, a foot or more in length. Most larvae crawl back to the tent at night, but forage out to feed during the day, defoliating increasingly larger portions of the branches and tree. Close up of tent with caterpillars
LIFE HISTORY: Winter is spent in the egg stage as one of many in a dark brown varnished collar or belt encircling the twigs. The young larvae hatch at or before bud growth in March or April and gather in a fork of the limbs to spin their large webby nests. The larvae leave during the day to feed, but return to the nest at night, or during rainy weather. They are full grown (2 to 2 ½ inches) in 4 to 6 weeks and often crawl to nearby buildings or protected places to spin their dirty white cocoon. The moths emerge in about 3 weeks and each female lays an egg collar (containing 150 to 350 eggs) around a twig. One generation per year. Overwinter in egg masses on small twigs.
CONTROL: Early control is important. However, it is difficult because larvae begin feeding on leaves unfolding from the bud before there is adequate leaf surface to be sprayed. Insecticides with residual effectiveness are desirable. Most will kill larvae hit by the spray, however, larvae in webs are protected from sprays. Treat foliage and twigs during the day. Webs can be flash-flamed at night with care not to get bark scorch or burning.
REMARKS: Larvae most frequently cause concern when migrating to protected places to hibernate. They crawl on other types of plants, roadways, walks, buildings, etc. Suggesting infestations elsewhere than on the host. No further feeding occurs when larvae are mature and migrate. Insecticides are generally ineffective against mature larvae.
