 Joe Boggs reported that the overwintered eggs of EASTER TENT CATERPILLAR (Malacosoma americanum) began hatching in southwest Ohio this past weekend. The overwintered eggs of the FOREST TENT CATERPILLAR (M. disstria) should be hatching soon. Although the two caterpillars are related, they have distinctly different appearances, hosts, and behavior.
Eastern tent caterpillars (ETC) are covered in short, grayish-white hairs and have a distinct, unbroken white stripe down their backs. ETC is an accomplished and prolific tent-maker producing highly visible silk nests in the forks of branches. Joe noted tents are only about 1-2" across and difficult to spot. The caterpillars prefer to feed on trees in the family Rosaceae, particularly those in the genus Prunus, such as cherries. They also occasionally feed on ash, birch, maple, and oaks.
Forest tent caterpillars are also covered in short grayish-white hairs; however, they have a row of distinct white markings running down their backs. These markings have been variously described as looking like "foot prints," or as being "keyhole shaped." The markings are flanked by cobalt-blue lines running the length of the caterpillars' bodies.
Forest tent caterpillars (FTC) will feed on a wide variety of deciduous trees including ash, sweetgum, oak, birch, cherry, aspen, elm, basswood, and sugar maple. Despite its common name, FTC constructs only rudimentary mat like silk nests on leaves or bark. The caterpillars congregate in colonies during early instar stages; however, later instars disperse from the colonies and become solitary feeders.
Both of these general defoliating caterpillars are capable of causing serious stress to their host trees. Leaves lost to caterpillar feeding this spring must be replaced using energy stored from last season. Small ETC nests and congregated FTC colonies can be eliminated digitally using five-fingered "smash and/or smear" techniques.
Less hands-on methods include applications of the naturally occurring bacterium, Bacillus thuringiensis (Bt), applied to early instar stages, as well as other insecticides listed for general caterpillar control in the OSU Extension Bulletin 504, "Insect and Mite Control on Woody Ornamentals and Herbaceous Perennials" [ http://ohioline.osu.edu/b504/index.html ]. The tiny cats may only meow now, but they will roar later in the season! For more information, see: 
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