Most of us are aware of the patches of dead grass that began appearing on Victory Memorial Drive during the spring of 2021. Since that time, damage has also been seen on many neighborhood lawns. The damage is caused by the larvae (grubs) of the invasive European Chafer Beetle.
The pest is on the radar of the Minneapolis Parks and Recreation Board (MPRB) and management and restoration projects have begun on the parkway.
If your lawn is affected and you would like to prevent damage or simply learn more about the pest, the Victory Neighborhood Association (ViNA) is hosting a turf grass seminar. On Tuesday, August 13 6:30-7:30 p.m. Anoka County Master Gardener Kim Sullivan will present in the Victory Neighborhood on behalf of the University of Minnesota Extension’s Turfgrass Science team. She will share information about the European Chafer Beetle, what to do about the grubs and when to do it. She’ll also discuss timely lawn-care that should be done in late-August or early September to help make turf resilient to grub damage.
And since turf-free ground is a good starting point for new garden beds, ViNA’s Environmental Committee will share information about converting turf to landscape that is less likely to be affected by grubs and is beneficial to wildlife and water resources.
The pest was first discovered in Minnesota, in a lawn in south Minneapolis, in August of 2020. It first appeared in a nursery in Rochester, New York in 1940 and from there it migrated to New Jersey, Connecticut, Massachusetts, Rhode Island Ohio, Delaware, and the lower peninsula of Michigan. It showed up in Door County, Wisconsin in 2016 and now is in our neighborhood.
The mature European Chafer is about ½ inches long and tannish to red in color. It resembles a June bug but is smaller and lighter in color. The adults emerge from the soil in mid-June to early July around dusk on warm clear evenings to mate around shrubs and trees and return to the soil. But the adult chafers are not the problem, as they do not eat at all. After mating they lay their eggs in the top two to four inches of the soil and these eggs generally hatch within two to three weeks. It is the larvae in the soil that feeds on the turfgrass roots; they can do much more damage than Japanese beetle grubs because they spend a larger portion of summer feeding on turfgrass roots.
The grubs (larvae) over-winter in the soil just below the frost line. As the ground thaws in spring they return closer to the surface and continue to feed. In late spring and early summer they descend back in the soil to pupate and then emerge as the adult beetles ready to repeat the cycle.
The European Chafer grubs are ¼” to 1”, C shaped with a dark brown head and obvious legs. The larva is very similar to Japanese and May/June Bug beetles and may require an entomologist to identify.
So what kind of treatment can you use if you suspect that your lawn has been invaded by or may be susceptible to the European Chafer? Since it is relatively new in Minnesota we can turn to our neighbor, Wisconsin, who has been dealing with this pest since 2016. Non-chemical treatments are to water and fertilize turfgrass areas optimally to help them tolerate white grub feeding. The grubs thrive in dry conditions; one reason they were able to do so much damage in our last few summers of drought. In addition, be sure to mow at the correct height and at the correct frequency to encourage deep root growth. According to the University of Wisconsin Extension website, insecticides are the main way to deal with large infestations of grubs. (High infestations are more than five grubs per square foot of turf.) Not all insecticides will work and even those which are effective won’t work if applied at the wrong time. The next opportunity to control the grubs will be mid-August to early-September.
There are two types of insecticides, preventatives and curatives. Preventive insecticides are very effective in controlling small grubs and provide long lasting protection. They are most effective against smaller grubs so the preventive insecticides should be applied when the beetles are actively mating and laying their eggs. (Late May to late July; warmer temperatures speed growth and there is potential for more than one hatch in warmer years.) Curative insecticides are not long lasting and only effective when summer and late grubs are present and actively damaging the turf. Insecticides can come in granular or liquid form but whichever form is used, it must be well watered into the turf line where the grubs are actively feeding. The types of insecticides and how to apply them can be found in the “Controlling European Chafer in the Summer Months” bulletin at extension.wisc.edu
Learn more by joining us on Tuesday, August 13 from 6:30-7:30 p.m. behind the Lincoln Statue and near the intersections of Victory Avenue and 45th Avenue North. All are welcome; bring a lawn chair or other seating.