Japanese beetles are back chewing up plants in Johnson County — Here’s what you can do

Japanese beetles, a growing Kansas phenomenon, came back out to feed this summer. The small green bugs favor roses, linden trees, grapes and green beans. Image from K-State Research and Extension website

Johnson Countians might have spotted some small green and metallic-looking bugs around their yard this summer. Or seen the damage they can wreak.

What’s going on? With summer comes a surge of Japanese beetles, which have once again emerged in Kansas this time of year.

  • While they can be a nuisance in gardens, the K-State Research and Extension Office of Johnson County says by mid- to late July, we have typically seen the worst of them for the summer.

What are they? Japanese beetles are typically half an inch long, green and metallic-looking with coppery wings.

  • This species of beetle started showing up in the Kansas City area roughly 20 years ago, and it was ab0ut 10 years ago that they started appearing in Johnson County, according to the Extension Office.

When are they most common? Japanese beetles start to emerge in late June to feed on plants, and their activity usually starts to diminish by early August.

  • Dennis Patton, horticulture agent at the K-State Research and Extension Office, said the annual numbers of them have increased over the years.

What do they eat? Japanese beetles feed on more than 300 species of plants.

  • Some of their favorites include roses, linden trees, grapes and green beans.
  • Patton said while many plants with leaves will recover, the beetles do the most damage on vegetable garden plants.
  • “In perennial plants, (the damage) is cosmetic,” he said. “But on green beans in the vegetable garden, they’ll pretty much decimate the plants and eat the green bean pods.”

How do you get rid of them? One of the main ways to get rid of Japanese beetles is to shake them off plants into a jar of soapy water.

  • They can also be killed with Japanese beetle traps, with have a pheromone in them to attract the beetles.
  • However, Patton said the traps can sometimes do more harm than good on suburban properties.
  • “If you put one of these in your yard, you actually may be bringing more into your yard than you’re actually going to trap,” Patton said.
  • Various insecticides can also do the trick.