Written by: Alyson Buchanan, Colorado Master Gardener, 2023

The Japanese beetle is an insect that causes significant damage to both turfgrass and landscape plants. Recently this insect has made its way to the Front Range of Colorado and is poised to wreak havoc in our landscapes.

Life stages of the Japanese beetle. From left to right: egg, larva (stage I), larva (stage II), larva (stage III), pupa, adult. Photograph courtesy of David Shetlar, the Ohio State University.

What to lookout for: 

• Adult Japanese beetles are oval shaped, about 7/16-inch long, metallic green in color with coppery-brown wing covers, have antennae that are clubbed at the end, and have five patches of whitish hairs along their sides. Adults feed on leaves, buds, and flowers of many garden and landscape plants.
• Japanese beetle larvae are a type of white grub with a creamy white, C-shaped body, a dark head, and legs on the thorax that are well developed. The larvae feed on the roots of grasses.

Effective ways to control the insect: 

• Adults are best controlled by handpicking or using certain insecticide sprays.
• Larvae are best controlled by using certain insecticides or by insect parasitic nematodes.

For more detailed information including the list of recommended insecticides, see CSU Extension Fact Sheet 5.601 at https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/ 

Source: CSU Extension Fact Sheet 5.601