More bad news on the invasive pest front. On August 10, 2020, the Minnesota Department of Agriculture (MDA) announced that European chafer beetle (Amphimallon majale; Order: Coleoptera, Family: Scarabaeidae – Scarab Beetle Family; synonym – Rhizotrogus majalis), a non-native and highly destructive pest of turf, has been found in Minnesota. The beetles were reported to a University of Minnesota entomologist by a south Minneapolis resident who noticed swarms of beetles in their yard at dusk. The find was subsequently reported to the MDA and the identity of the insects was confirmed by the MDA with the assistance of the United States Department of Agriculture (USDA). As the common name suggests, the European chafer beetle is native to Europe and was first documented in North America when a larva was found in a nursery in New York State eighty years ago in 1940. Unfortunately, it appears this destructive pest has found its way to Minnesota.
About the same size as Japanese beetles (Popillia japonica), but typically smaller than our native May/June beetles/June bugs (Phyllophaga fusca, northern June bug, and other species), European chafer beetles look very similar to May/June beetles, but, in addition to being a little smaller (about a half-inch long and usually about two-thirds the size of May/June beetles), are light brown in color instead of reddish-brown like May/June beetles. Comparatively, Japanese beetles have iridescent, copper-colored elytra, a green thorax and head, and distinctive tufts of white hairs that stick out from under the wing covers along the sides of their abdomens. Of course, as most nursery and landscape professionals and many homeowners are well aware, Japanese beetles are another introduced pest that was inadvertently introduced to North America in the early 1900s.
Unlike Japanese beetle adults that feed on trees and shrubs and can cause significant damage by feeding on the foliage, flowers, and fruits of more than 300 species of plants, European chafer beetle adults do not feed and the larvae only feed on the roots of grasses including turfgrass. European chafer beetles may, in fact, be the most damaging scarab beetle/white grub pest of managed turf, and especially low-maintenance turf, because the larvae feed on the roots of turf later into the fall and resume feeding earlier in the spring than the larvae of other scarab beetles including Japanese and May/June beetle larvae. According to the MDA, home lawns, golf courses, and turf growers could be significantly impacted if the European chafer beetle becomes established in Minnesota.
Similar to the damage caused by the larvae of other scarab beetles, the damage caused by European chafer beetle larvae appears as irregular patches of yellowing and dying turf, which can be extensive when infestations are large. Most of the damage caused by the feeding of European chafer beetle larvae occurs in late fall and in the spring just before pupation and the subsequent emergence of the adult beetles. Poorly managed, stressed lawns tend to be more susceptible to infestation and damage. The larvae of all scarab beetles, including European chafers, are typically referred to as white grubs and the larvae of different species look very much alike – white to cream colored with brown heads, a translucent lower abdomen that shows the dark-colored contents of the gut, and bodies that are oriented to form a C-shape when at rest.
Unlike May/June beetles which have a three-year life cycle, but the same as Japanese beetles, the European chafer beetle typically has a one-year life cycle. Adult beetles emerge from the soil in late spring and early summer (mid-June/July, but the timing can vary from year to year depending on soil temperatures) and mate in swarms on broadleaved trees and shrubs on warm evenings and nights during their one to two-week lifespan. It was this swarming activity that was observed by the homeowner in Minneapolis. After mating, the female beetles typically deposit 20-50 eggs individually in the soil (several inches deep) where they hatch in two to three weeks. The developing larvae feed on the roots of grasses and pass through three larval stages (instars) for the remainder of the summer and fall until the soil freezes (November; at this time, the grubs move deeper into the soil profile and overwinter below the frost line). The larvae continue feeding after the soil warms up again the following spring before they pupate, undergo metamorphosis, and emerge as adults completing the cycle. A variety of animals including racoons, skunks, foxes, shrews, moles, and birds feed on the grubs and can also cause significant damage to infested lawns as these predators search for grubs.
Because the European chaffer beetle is a serious pest that is new to Minnesota, and because the extent of its distribution in the state is unknown, the MDA would like Minnesota residents, including nursery and landscape professionals, to report suspected finds of the European chafer beetle to the MDA’s Arrest the Pest Line at 1-888-545-6684 or firstname.lastname@example.org (mailto:email@example.com). If possible, samples should be collected and photographed and placed in Ziplock-type bags and put in the freezer for future identification if needed.
The MDA news release announcing the discovery of European chafer beetle in Minnesota is available at https://www.mda.state.mn.us/destructive-european-chafer-beetle-discovered-minnesota and additional information about the European chafer beetle, is available on the MDA website at https://www.mda.state.mn.us/plants-insects/europeanchafer.
Other resources that may be of interest include:
European Chafers, Japanese Beetles and Their Damage to Lawns; David Chinery, Cornell Cooperative Extension, 2016; https://s3.amazonaws.com/assets.cce.cornell.edu/attachments/15667/European_Chafers__Japanese_Beetles_and_Their_Damage_To_Lawns.pdf?1464106751
Best Management Practices for European Chafer Beetle; Metro Vancouver and the Invasive Species Council of Metro Vancouver, 2019; http://www.metrovancouver.org/services/regional-planning/PlanningPublications/ChaferBeetle_BMP-v6.pdf
Turfgrass Insects: Managing White Grubs in Turfgrass; Douglas S. Richmond, Purdue University Extension – Entomology, 2016; https://extension.entm.purdue.edu/publications/E-271/E-271.html
If you have questions or comments regarding this MNLA Regulatory Update, contact Jim Calkins, MNLA Regulatory Affairs Manager, at firstname.lastname@example.org or 952-935-0682.