UNL educator gives advice on protecting plants against Japanese beetles

LINCOLN, Neb. (KLKN) – Japanese beetles are currently at the height of their feeding season, which is expected to continue into late August.

The invasive species from Japan start as grubs in the soil, then come up to feed on local foliage like soybeans.

Methods for dealing with Japanese beetles include spraying with pesticides, using store-bought Japanese beetle bags and individually picking the beetles off the plant and placing them into soap water.

UNL Extension Educator Kait Chapman recommends the soap water method, by placing a bucket full of soap water at the base of a plant and patting it down, causing the beetles to fall into the bucket.

She said that the use of Japanese beetle bags is counterproductive in tackling the issue, as it can cause more beetles to gather in the cleared-out space.

“If you want to treat for grubs, the best time to do that is June and July, right when they’re at the surface of the soil,” Chapman said.

Some pesticides can also be counterproductive, she said, because they also kill insects that eat the same plants that Japanese Beetles do. So they also kill the beetles’ competition.

“In Japan, where they are from, they’re not reaching pest status because they have all those natural enemies,” Chapman said.

The beetles have no local predators, which has caused them to reach pest status in Nebraska. Chapman said local birds occasionally feed on the bugs, but they are not a part of their natural diets.

The beetles’ presence in America can be traced back to a shipment of Japanese iris bulbs in 1912 that contained some of the beetle grubs.