Japanese Beetle

What it does

Adults feed in groups on warm, sunny days, chewing leaf tissue between the veins and leaving a lacy, skeletonized look, and also feeding on flowers and fruit. Feeding beetles release odors that attract still more beetles, so damage snowballs. Below ground, the white grubs chew grass roots, producing dead, spongy lawn patches.

Where it lives

An invasive species first found in New Jersey in 1916, it is now established across the eastern US and parts of the Midwest and is spreading westward. Adults feed on over 300 plant species in gardens, orchards, and landscapes, while the grubs live in the soil of lawns, pastures, and turf.

How it breeds

Adults emerge in early to midsummer, feed, mate, and lay eggs in the soil of lawns. The grubs hatch and feed on grass roots through late summer and fall, overwinter deep in the soil, then feed again briefly in spring before pupating. There is one generation a year.

What it eats

Adults eat the leaves, flowers, and fruit of hundreds of plants (roses, grapes, lindens, fruit trees, and more); the grubs feed on the roots of turfgrass and other plants.

Identification

Adults are about 1/2 inch, shiny metallic green on the head and thorax with copper-bronze wing covers, and, uniquely, five small tufts of white hairs along each side plus two on the tip of the abdomen. Grubs are white, C-shaped, with a brown head, found in lawn soil.

Signs of an infestation

• Metallic green-and-copper beetles clustered on plants
• Leaves skeletonized to a lacy network of veins
• Chewed flowers and fruit in mid-summer
• Brown, dead patches of lawn that lift up easily
• White C-shaped grubs in the soil under damaged turf

Prevention tips

• Handpick beetles into soapy water in the early morning
• Avoid pheromone traps near plants, they can attract more beetles
• Keep lawns healthy; treat grubs only where they are damaging turf
• Protect prized plants with fine netting during peak flights
• Choose plants Japanese beetles tend to avoid for new plantings

Professional solutions

Home gardeners manage adults with hand-picking and netting, and lawns can be treated for grubs when counts are high. For persistent turf damage, a local extension office or lawn-care professional can advise on properly timed grub control, including milky spore or beneficial nematodes, and on labeled insecticides applied to protect pollinators.