Forest Health Fact Sheet: Forest Tent Caterpilar

Native to North America, the forest tent caterpillar is widely distributed from Canada to Florida, and its range extends west to the Rocky Mountains.  Contrary to its name, this insect does not make a tent, rather, the caterpillars make a silk mat on which they congregate.  This insect has one generation per year, and feeds on a wide variety of deciduous hosts – especially oaks and gums in the Southeast.  Outbreaks occasionally occur, and these insects can completely defoliate mature trees.  The trees will usually survive, but successive defoliations can weaken the tree.  Adults are about 1½” wide and are yellowish-brown.  Eggs are laid in rings around twigs, and spend the winter in this stage.  Caterpillars hatch in the spring, can grow up to 2½” long, and can be identified by their blue head, row of yellow dots along the back, and bluish sides.  Older caterpillars tend to wander in search of places to pupate, and during this time can become nuisance pests to homeowners.  Larvae have been known to cover the sides of houses, and the frass (excrement) can make sidewalks slippery.   Several natural enemies, including other insects and viruses, help manage populations, and insecticides or cultural control methods may be used on high-value trees.