The webs we're seeing in many trees now are Eastern tent caterpillars. Over the next two weeks, they will hatch and begin migrating," Brown noted. The caterpillars may completely defoliate ornamental cherry and apple trees but the leaf loss will rarely kill them. The primary problems caused by tent caterpillars are the unattractive appearance of the webs amid the surrounding beauty of spring and the nuisance of migrating caterpillars." Brown said the other tree pests, gypsy moths, are quite small now but will feed on oaks and other trees until early June. "The gypsy moth population is heaviest this year in parts of Bergen, Burlington, Hunterdon, Morris, Ocean, Passaic, Salem, Sussex and Warrant counties," Brown said, "and the department began this week to treat about 8500 acres in 23 municipalities around the state." Of the two tree pests, the gypsy moth is the more serious since it defoliates large areas of woodlands and repeated attacks will result in tree mortality. Identifying which pest is plaguing your trees is simple, Brown pointed out. "Gypsy moths don't construct webs." John Kegg, Chief of NJDA's Bureau of Plant Pest and Disease Control, added, "Gypsy moth caterpillars have blue and red dots on their backs but tent caterpillars have a single white line down the middle of theirs." Kegg suggested that it's best to try to control both kinds of caterpillars while they are still small and living in the host trees. "Once they reach an overall length of about two inches, they'll start to migrate and become more difficult to control. "The non-chemical insecticide, Bacillus thuringiensis (B.t.) is quite effective against both pests when applied to the leaves while the caterpillars are less than an inch long," Kegg noted. Clipping of webbed branches or crushing the caterpillars found in the webs can also reduce the Eastern tent caterpillar problem but doesn't work with gypsy moth larvae.