While out on a short lunch hike today, Aaron (our program director) noticed these greenish beetles swarming and mating in the tall prairie grasses near the lower parking lot of the Welty Environmental Center. This is just one stalk, but dozens of stalks just like the one pictured were covered in beetles.
With a little digging and use of a Peterson First Guide to Insects, we identified them as Japanese Beetles or Popillia japonica. These beetles belong to the scarab (Scarabaeidae) family. They are non-native insects to the Stateline Area and to the United States. Just as their name indicates, they are from Japan.
According to Wisconsin Horticulture, the Japanese Beetle “is considered the single most important turfgrass-infesting pest in the United States ” and they “ feed on foliage or flowers, and are a major pest of over 350 species of plants, including fruits, vegetables, ornamentals, field and forage crops, and weeds.”
The grubs feed primarily on plant roots. The adult beetle feeds on plant leaves. With Welty’s efforts to restore prairie grasses and flowers around the center, these little critters could reek a lot of havoc on the plants we want to foster. The Japanese Beetle has been observed to seek climates between 64 and 82 degrees Fahrenheit and winter soil of around 15 degrees Fahrenheit. With the Stateline Area’s warm spring this year and warmer (on average) winters, we should expect to see many many more.
To learn more about the Japanese beetle visit Wisconsin Horticulture. They have great details regarding life cycle, control, trapping, and removing this pest from your gardens. To learn more about non-native insects, you can visit Wisconsin Department of Natural Resources. The WI DNR also has a link for reporting invasive sightings.