WIUM Tristates Public Radio

Japanese Beetles are Taking Over This Summer

Jul 10, 2017

The Japanese beetle can be a dreaded insect for any gardener. They are easy to spot with their copper colored wings but they are not as easy to stop. 

Japanese beetles feed on just about every plant, their favorites being rose bushes, raspberries, and black berries.

Kari Houle, Extension Educator in Horticulture for the University of Illinois Extension office that serves Adams, Brown, Hancock, Pike, and Schuyler Counties, said the invasive pest is abundant this summer.

“Any of our exotic pests that come here,that do cause a lot of destruction -- there are not a lot of natural predators. People’s chickens will eat Japanese beetles but I don’t think the chickens can out eat the amount of Japanese beetles," Houle said.

"So that’s a lot of times what we see with other invasive insect pests (such as) Emerald ash borers on ash trees. There are really no natural predators here to help keep that population under control.”

Houle said chemicals will kill the beetles but you need to take caution when applying chemicals to plants. Most will also kill off pollinators such as bees and butterflies.

She also advises against using Japanese beetle traps.

Japanese Beetle damage on roses.
Credit Kari Houle / University of Illinois Extension

“Japanese beetles aggregate by releasing pheromones -- that's how they come together. Those traps use the same concept to draw them in, so you might be dumping those Japanese beetle traps constantly but you are actually encouraging more to show up in your yard," she said.

Houle suggested using a bucket of water with a couple drops of dish soap to kill the beetles. She said to knock them into the bucket and they will drown, but be sure to empty the bucket so they don’t attract others with the pheromones released.

While mild weather in February seemed nice at the time, Houle said cold winters are the best bet for controlling Japanese beetle populations.