gypsymoth.wi.govSpongy Moth Resource Center

Turn on more accessible mode Turn off more accessible modeWisconsin.Gov Agency Directory Online Services State of Wisconsin Spongy Moth (Lymantria dispar) Resource CenterSearch The Insect Identification Common lookalikes [PDF] Is spongy moth present in my area? Natural enemies Control Options Options for homeowners (management calendar) Insecticide treatments for yard trees Options for foresters and those with 10+ acres Predicting next year’s damage Aerial Spraying DNR and DATCP spray block maps and information Organizing an aerial spray [PDF] Find an aerial applicator Regulations Quarantine and regulations Avoid moving spongy moth [PDF] Wisconsin firewood rules Get Help Find a forester Find an arborist HP Alert Content ​The State of Wisconsin ​does not offer a​ state-sponsored or cost-share program for citizens to sign up their property to be treated to prevent defoliation by spongy moth.​ ​ Feature_Img Wisconsin DNRWelcome! Agency_Content The Spongy Moth Resource Center is the central location for information and resources related to spongy moth for Wisconsin residents and landowners. Participating State A​​genc​​ies Department of Agriculture, Trade and Consumer Protection (DATCP) Department of Natural Resources (DNR) University of Wisconsin-Madison Extension (Extension) CTA_Image1 Yard Tree Management CTA_Content1 ​Homeowners who want to protect one or a few trees from spongy moth should consult with a certified arborist for more information. Some options include spraying insecticides, scraping egg masses off surfaces or trapping them using sticky barriers. linky-01 Learn more CTA_Image2 Woodlot Management CTA_Content2 ​Woodlot owners should consult with a forester prior to beginning management. Some available options include doing a private aerial spray of the property or using active forest management to decrease defoliation impacts by improving tree health. linky-02 learn more CTA_Image3 State & Fed. Quarantines CTA_Content3 ​The quarantine covers 53​ of Wisconsin’s 72 counties primarily in the eastern 2/3 of the state. Under quarantine regulations, wood product and outdoor household items must be inspected or certified before moving them from quarantined to non-quarantined areas.​ linky-03 learn more Content_Area1 Frequen​tly Asked Questions View all questions and answers in PDF format. ​ 1. ​What is spongy moth, and why are they harmful? Spongy moth ( Lymantria dispar ) is one of the most important forest and shade tree pests in the eastern United States. Approximately every eight to 10 years, spongy moth populations can have an outbreak period during which the population is very high, and trees can be stripped of their leaves (defoliated). Large numbers of spongy moth caterpillars can completely defoliate (eat the leaves) of a tree in a short period of time. Repeated defoliation can weaken trees, resulting in greater susceptibility to disease and other pests. Spongy moth caterpillars can also be a nuisance when they congregate on the sides of buildings or produce large quantities of frass (droppings) that fall from trees onto lawns, patios and sidewalks. The hairy caterpillars can cause rashes, welts and other irritation if touched. Additional resources: DATCP: Fact sheet on spongy moth​ DNR: Fact sheet on spongy moth​ Extension: Learn to identify spongy moth DNR: Tell the difference between spongy moth and other defoliating caterpillars ​ Spongy moth caterpillars feed on tree leaves from April or May through July. / Photo Credit: Wisconsin DNR ​ ​ 2. How does spongy moth spread, and how can I help stop it? While spongy moth is a common pest throughout the eastern United States, including Michigan and the eastern three-quarters of Wisconsin, it has yet to establish in many areas of western Wisconsin ( see the current Wisconsin spongy moth quarantine map ). Adults, caterpillars, pupae and egg masses can be moved long distances when attached to firewood, potted plants, Christmas trees, outdoor furniture, vehicles, trailers and anything else stored near trees. Accidentally moving one egg mass to a non-quarantined county can give rise to new spongy moth infestations. Check your vehicles, trailers or outdoor items for spongy moth life stages when you are in an area where spongy moth is present. When obtaining firewood, either buy it where you’ll burn it, buy certified treated firewood or gather it on-site (where permitted). Additional resources: DATCP: Precautions to avoid moving spongy moth (PDF) DATCP: Information about spongy moth quarantine and regulations DNR: Wisconsin firewood rules and resources External: Responsible firewood practices Spongy moth egg masses attached to firewood. / Photo Credit: Wisconsin DNR 3. Will a spongy moth infestation kill my tree? Healthy hardwoods generally can endure one or two years of heavy defoliation (around 60-100% of leaf loss) before tree mortality occurs. Healthy trees will normally put out a replacement set of leaves a few weeks later (see photo), though the new leaves may be smaller and lighter in color. A heavily defoliated tree must use its energy reserves to grow a replacement set of leaves. This weakens trees and makes them more susceptible to disease, drought stress and other insect attacks, which in combination can kill the trees. You can help valued trees recover from defoliation by watering them deeply each week if there hasn’t been a soaking rain. Keep watering the tree until it has dropped its leaves in the fall. Trees generally need the equivalent of 1 inch of rain per week. Also, avoid giving trees any nitrogen fertilizer as this will overstimulate the tree to produce more replacement leaves than it can support. That may deplete food reserves so much that the tree won’t be able to produce leaves the following spring. Trees most likely to be heavily defoliated include oak, apple, birch, aspen, willow, tamarack and linden. Other deciduous trees and conifers also can be stripped of leaves or needles. If you remain alert to increasing numbers of caterpillars and egg masses, use management options to reduce damage to your trees and provide adequate water through the growing season, you can greatly reduce the chance of your tree dying. Additional resources: Extension: Year-round homeowner’s guide to managing spongy moth Extension: How to predict next year’s spongy moth damage A tree after complete spongy moth defoliation (left) and leaf regeneration about a month later. / Photo Credit: Wisconsin DNR 4. What does it mean for a Wisconsin county to be quarantined for spongy moth? As of April 2023, the spongy moth quarantine covers 53 of Wisconsin’s 72 counties. Under quarantine regulations, wood products and outdoor household items must be inspected or certified pest-free before being transported from quarantined areas to non-quarantined areas. Quarantine regulations apply to both businesses and private citizens. Quarantined counties have well-established populations of spongy moth, even if they aren’t at levels noticeable to casual observers. Non-quarantined counties may have patchy low-level populations, but the pest is not well-established Additional resources:​ DATCP: More information about spongy moth quarantine and regulations Don’t Move Firewood: Information on preventing the spread of spongy moth on firewood​ A map showing Wisconsin’s spongy moth quarantine counties (in red). / Map Credit: Wisconsin DATCP 5. Are there natural enemies of spongy moth? In areas where spongy moth has been established for several years, natural enemies can help keep spongy moth populations in check. Natural enemies include insect parasitoids that attack eggs and caterpillars, predators such as birds and mice, and insect-specific pathogens. There are two common pathogens that affect spongy moth caterpillars and usually bring an outbreak to an end: Nucleopolyhedrosis virus (NPV) and Entomophaga maimaiga . NPV is a virus that causes caterpillars to die and hang from trees in an inverted V” orientation....