Three varieties of leaf-eating caterpillars hit the Granite State in the last few weeks. Here's an update on what to look for, what to worry about and what not to worry about.

Eastern tent caterpillars are the most visible. They weave those unsightly webs, mostly in cherry trees, stripping the tree bare. They are more of a nuisance than a threat to trees, rarely killing healthy trees. They have nearly completed feeding and will soon pupate, emerging as moths in July. Expect defoliated trees to send out new leaves once the feeding stops.

Forest tent caterpillars are the "tent caterpillars" that don't make tent-like nests. They are active now, defoliating oaks throughout the state. They feed on other hardwoods including sugar maple. Like their relative, the eastern tent caterpillar, they don't cause irreparable harm to healthy trees.

Gypsy moth is also starting to feed. Because most of us remember the extreme defoliation this pest caused in the 1980s and 1990s, this caterpillar gets blamed for most of the work of the other two. Happily, a fungus introduced in the early part of the last century is preventing gypsy moth numbers from exploding. Though it is currently among us, it is unlikely the gypsy moth will defoliate as extensively as they did the past.

Populations of insects rise and fall with the controls in nature that keeps them in check. Insect parasites, predators, viruses, fungus, weather extremes, and even starvation when populations exceed the food supply, all help control them. There is little we can do to prevent them from attacking, though there are some effective treatments for specimen trees. For more information on appropriate treatments, call the toll-free Info Line at our Family, Home & Garden Education Center, 1-877-398-4769.

Trees have adapted to occasional defoliation and other stresses. No doubt, trees do better without being stripped of their leaves, but they are amazingly resilient and healthy trees recover as long as they aren't defoliated yearly.

By Karen Bennett, UNH Extension Forest Resources Specialist