It’s almost over! The Gypsy Moth frass, leaf fragments and large, hairy caterpillars will stop raining down on your head and home in the next few days, if they haven’t already. The only damaging and very messy part of the Gypsy Moth life cycle is the caterpillar phase, and this is the only stage of the life cycle that eats anything. Let’s repeat that. Only the caterpillars eat. The pupae, adult moths, and egg masses do not eat. Anything. Ever. The caterpillars will begin pupating within the next week or two, and the feeding/defoliation will stop for this year. If you have hiding bands installed, we encourage you to leave them in place for another few weeks to encourage the adult moths to lay their egg masses there, facilitating your later removal.
How about my trees? The vast majority of trees, even those heavily defoliated by caterpillar feeding, will be fine. Deciduous trees lose their leaves every year, anyway, albeit not typically so early in the season. Bare trees that were healthy before the invasion will remain bald for a few weeks before they flush a new set of leaves to replace those eaten by the caterpillars. During this time, unscrupulous contractors may try to convince you that your trees need to be treated with a pesticide or that they are dead and should be cut down before they fall. Again, most trees will be fine, and it is far too soon to call time of death as it can take weeks, months, or even years to determine outcomes. If you are able to water valued individual trees, we recommend that you do so to help them recover. The dry conditions we’ve had this season are not doing our trees any favors. Avoid damaging trees! Lawn mower crashes, string trimmer nicks and root compaction are real tree-killers even when they don’t have drought stress and Gypsy Moth caterpillars gnawing on them. Evergreen trees heavily defoliated by Gypsy Moth caterpillars are not as lucky as deciduous ones and are unable to produce a new set of needles all at once. Please contact your local MSU Extension office if you have concerns or questions about tree health.
1 – Gypsy Moth pupae – Female (Top), Male (Bottom)
Photo Credit: Milan Zubrik, Forest Research Institute – Slovakia, Image 1370017. Forestryimages.org
2 – Adult moths (Left: Male, Right: Female)
Photo Credit: USDA APHIS PPQ Archive. Image 2652079. ForestryImages.org
3 – Gypsy Moth egg masses with a half dollar coin
Photo credit: Kirsten Lyons, Columbus Twp., February 2021
4 – Gypsy Moth caterpillars on hiding band
Photo credit: Patty Troy, Clyde Twp., June 2021
What’s next? The caterpillars will pupate, forming a brown, approximately one and a half (males) to two and a half-inch (females) long cocoon around themselves, emerging as adult moths about two weeks later. The moths will mate, lay egg masses and die. The egg masses will persist until next spring, when they will hatch as tiny caterpillars and start the life cycle again. Cocoons, female moths (which cannot fly), and egg masses could be anywhere you’ve found caterpillars. Male moths, with their lovely, feathery antennae, will find pheromone-emitting females and fly to them to mate. Lap siding, rough tree bark, stacks of firewood, and RV’s seem to be favored locations for egg mass laying. Some of these help to explain how Gypsy Moth gets its name. As if “ballooning” caterpillars weren’t enough to spread them, all life stages also get around by hitching a ride on campers or other mobile objects, and new infestations are often started unwittingly by recreationists. Don’t be one of them.
About those hiding bands…and egg masses. We recommend leaving your burlap hiding bands in place to encourage moths to lay their egg masses there, making them easy to spot during fall egg mass surveys and LATER egg mass scraping. Remember, egg masses must be present to be counted in egg mass surveys. Egg mass surveys are used to determine where cooperative management actions, such as aerial sprays, should be implemented. Unless they’re on something you plan to relocate, it’s also important to leave egg masses in place until early spring so that the natural enemies that prey on eggs can feed on them, reducing the numbers of viable eggs and allowing the natural enemies to complete their life cycles.
Report the furry little monsters! If you haven’t already reached out to your municipal and county officials about your Gypsy Moth woes, please do so now so that they can gauge the extent, locations and severity of this community challenge. They will ask for your name, address, email, phone number, abundance/density/health of caterpillars, number of egg masses, acres of property and amount of defoliation, and may also inquire about what you had for lunch (kidding–probably not). This information will be needed for later defoliation and egg mass surveys. We further encourage you to report your observations on the Midwest Invasive Species Information Network (MISIN) website or smartphone app (www.misin.msu.edu/). That shows natural resources agencies, researchers, and citizen scientists how the infestation is unfolding across the state and region and how we’re comparing locally.
More Gypsy Moth resources:
Our earlier blog post, Gypsy Moth – An unwelcome start to summer
Michigan State University Gypsy Moth resources
Friends of the St. Clair River and the Lake St. Clair Cooperative Invasive Species Management Area are partnering to deliver public education and raise awareness of local invasive species issues such as Gypsy Moths. Reach out to us at www.scriver.org with questions and for more information.
Kirsten lives in a ramshackle farmhouse in rural China Township with her husband, three spoiled cats and four pet chickens. She is inordinately proud of the fact that Giant Swallowtail butterflies, Five-lined Skinks and Red-bellied Snakes also call her place home.
Do you have nature stories or observations you’d like to share? Leave us a comment!