Tuesday, May 15, 2018

Japanese Beetle Facts and Resources

Japanese beetle on roses, photo courtesy Whitney Cranshaw, CSU
For close to a century, the Japanese beetle (Popillia japonica) has been one of the most seriously damaging insect pests of both turfgrass and landscape plants over a broad area of the eastern US. Recently, there have become a few permanent, reproducing populations in some communities along the Front Range of Colorado. 

Japanese beetle larvae, photo courtesy David Shetlar, Ohio State University
The Japanese beetle is generally metallic green with coppery-brown wing covers, which do not completely cover the tip of the abdomen. Along the sides are five patches of whitish hairs. The larvae are a type of white grub that feeds on the roots of grasses. They have a creamy white body with a dark head. Normally the body curves into a C-shape.

The Japanese beetle has a one year life cycle. Adults may begin to emerge from the soil in early June and are usually most abundant in early summer – from late June through early August. The larvae become nearly full-size by early September and their rapid development during late summer can cause turf damage. 

Japanese beetles are damaging in both their adult and larval stages, although the type of injuries are different. Injury by the adults is more obvious and usually the primary concern in Colorado. Adults feed on leaves, buds and flowers of many garden plants, including roses. Larvae feed on roots of grasses, producing root pruning that limit the plant’s ability to acquire water.

Control of adult Japanese beetles can include trapping, hand picking and insecticides. Control of the larvae in lawns includes cultural controls, biological controls and insecticides. 

For an in-depth description of the Japanese beetle and detailed instructions on control, refer to Japanese Beetle Fact Sheet 5.601. The fact sheet includes additional information on the life cycle, damage, and control options, including specific insecticide recommendations and cautions.

For additional information:
Japanese Beetle in Colorado, Colorado Dept. of Agriculture