Once the snow had melted and the grass began to green up it became very apparent that the European Chafer Beetle is still very active in our area, not only on the parkway but in a great number of home lawns. The evidence is in the large patches of dry, brown and dying grass, mostly near trees. This has also been a big topic of conversation on social media as people lament the loss of their lawns and ask for advice as to how to deal with it.
The real culprits are not the beetles themselves but their grubs that feed on the grass roots. The dead, brown lawns this year are the result of the beetle activity last summer (or perhaps even two summers ago). Those of us who have so far escaped the beetle damage would be wise to treat our lawns this year in order to prevent the beetle grubs from destroying our lawns over the next year.
The European Chafer Beetle was only discovered in Minnesota, in a lawn in south Minneapolis, in August 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 Michigan lower peninsula. It showed up in Door County, Wisconsin in 2016 and then raised its ugly head in Minnesota.
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 small trees, and return to the soil. This makes their activity hard to detect. Their mating activity is temperature-dependent and not all of them emerge at once. But the adult Chafers are not the problem, as they only live about three weeks and they do not eat at all during this time. 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 they leave 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 European Chafer grubs are ¼” to 1”, C-shaped with a dark brown head and obvious legs.
The grubs (larvae) feed most heavily from August through November and then 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 heavily from mid-March through May. 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. Turf damage is most severe in drought conditions which we experienced the last two years.
So what kind of treatment can you use if you want to prevent grub damage to your turf grass? The University of Michigan Extension Service, which has been dealing with this for more years than we have in Minnesota, recommends a couple of things. Frequent irrigation in the last two weeks of June makes the turf less attractive for the adult beetles to lay their eggs, and irrigation in the fall helps the grass survive root pruning by the grubs.
Insecticides containing the active ingredients imidacloprid, thiamethoxam, clothianidin or chlorantraniliprole are very effective against grubs when applied in June to mid-July. There are also organic treatments that may be used. These preventive treatments kill young grubs as they hatch, but do not work as well against larger, established grubs. Insecticides containing carbaryl or trichlorfon can be used as a curative treatment in late August, September, October, March or April.
Insecticide applications should be made after mowing your lawn to remove open flowers that might attract bees. All insecticide applications should be followed immediately with 0.5 inch of irrigation to move the insecticide into the thatch and root zone. Always wear rubber gloves, long pants and rubber boots when applying insecticides. Store leftover chemicals in the original container out of the reach of children and pets.
European Chafer is most damaging when it first becomes established in an area. After four to 10 years, the population falls to a level that grubs might be detectable, but damage is unlikely. With a little bit of care (and luck) some may be able avoid European Chafer Beetle damage to their lawns.