MADISON -- State forest health specialists report that populations of the native eastern tent caterpillar are active at least three weeks early this year in southern and central Wisconsin, due to warm weather.
Eastern tent caterpillar
Eastern tent caterpillar populations have been high in southern and central Wisconsin for several years. Their thick, white "tents" or "webs" are already visible in trees this spring and the young caterpillars are already growing and eating tree leaves.
"Eastern tent caterpillars are often confused with gypsy moth or forest tent caterpillars, but they are easily distinguishable," says Mike Hillstrom, forest health specialist at the Department of Natural Resources. "It is the only one of these species that makes a tent."
Eastern tent caterpillars have a distinctive white stripe down its back.
Eastern tent caterpillar tent.
The tents made by the caterpillars are found at the base of branches and are most often seen on roadsides or fencerows, or on open-grown trees. Eastern tent caterpillars favor crabapple, apple, wild cherry and wild plum trees though it also feeds on oak and some other deciduous trees. The caterpillars are typically done feeding by mid June but their tents will be visible until rain and wind eventually break them down.
Caterpillars are already active this year so now is the time to find and kill them when their tents are still small. The easiest, least expensive method is to put on a pair of rubber gloves or use a rake and scrape the caterpillars and tent into a bucket of soapy water. Do this in early evening after most of them have returned to the tent. The next morning discard the soaked tent and dead caterpillars. If the tent is out of reach or if you prefer, tear up the tent with a stick and spray the area with insecticidal soap (not dish soap) or a contact insecticide. Another alternative is to spray a Btk based insecticide on the leaves around the tent. When caterpillars leave the tent to eat the leaves they will ingest the Btk.
"Don't cut branches off of your tree to remove the tents. This causes much more damage to your tree than the caterpillars ever would," says Mark Guthmiller, forest health specialist with the Wisconsin Department of Natural Resources. "Also, do not burn the nets or webs out of the tree. This is dangerous and also kills the branches."
FOR MORE INFORMATION CONTACT forest health specialists in the following locations: Linda Williams, Green Bay, 920-662-5172; Mike Hillstrom, Wisconsin Rapids, 715-421-7825; Mark Guthmiller, Madison, 608-275-3223; Brian Schwingle, Rhinelander, 715-365-8908 or statewide forest health educator Colleen Robinson Klug, 608-266-2172