It’s June, and I’m getting an influx of calls related to plant identification, diseases, and insects. If you have a garden, you’re probably familiar with the Japanese beetle, which can cause significant damage to a wide variety of plants. This week, lets talk about these insects and what you can do about them.
As the name implies, Japanese beetles (Popillia japonica Newman) are not indigenous to North America. They were accidentally imported from Japan and first appeared in New Jersey in 1916. Despite efforts to contain them, they now infect about half of U.S. states and continue to spread each year.
Adult Japanese beetles are less than one-half inch long, metallic green with copper-brown wing covers, and are often found on plants in direct sun. An important identifying characteristic is the six small tufts of white hair along the sides of the abdomen under the wing edges. Females are typically slightly larger than males. They have a one-year life cycle with adults emerging in June. Each adult lives 30 to 45 days, during which time females lay 40-60 eggs in the soil. The grubs hatch after 8-14 days and spend 10 months underground, feeding on plant roots and organic matter until the next summer.
These beetles emerge from the ground in early June and feed on more than 300 different plants, including herbaceous ornamentals, shrubs, vines, trees, small fruits, fruit trees, row crops, and even poison ivy. Japanese beetles feed in masses, as they emit pheromones that attract other beetles to feed and mate. These beetles feed on the upper surface of plant leaves, eating the tissue between veins. This results in a characteristic “skeleton” appearance to the damaged leaves.
Japanese beetle larvae are a small white grubs that form a c-shape when disturbed. Larvae can cause significant damage to the roots of turfgrass. If you’re concerned about larval damage of turfgrass, give our office a call for control recommendations.
There are a few options for control and management of Japanese beetles in the garden. Some plants are more susceptible to these pests, specifically roses, Japanese maple, fruit trees, and crape myrtle. Others are less desirable such as magnolias, redbuds, dogwoods, holly, and hydrangea. Planting a variety of things in your garden can help reduce insect damage. Also, be sure to remove diseased and damaged fruit from trees and the ground, as it can attract Japanese beetles. If you catch them early and don’t have too many, hand-picking is an effective control. Simply pick or shake off the beetles and drop them in a bucket of soapy water. This is easiest to do in the early morning when the beetles are less active. Just a note – pheromone traps are not recommended for controlling Japanese beetles. They do trap beetles, but in doing so, they attract many more beetles to your yard and garden than would ordinarily be there.
Both larvae and adult Japanese beetles can be controlled with pesticides. Short-residual insecticides like Sevin can be sprayed on foliage and flowers of landscape plants to manage adult beetles. During periods of heavy activity, you may need to spray every 3-5 days, and we recommend spraying during the hottest part of the day (12-5PM) to reduce impact on pollinator species. If you use Sevin on vegetables or food crops, you need to wait 5 days before harvesting. If you have an issue with Japanese beetle larvae in your lawn, long-residue insecticides can be applied to the soil in early summer next year to control grubs. Be sure to read and follow all label instructions on pesticides BEFORE using them in your landscape to ensure proper safety, insecticide use, rate of application, and compliance with any restrictions.
Despite their prevalence, Japanese beetles can be effectively managed with cultural and chemical controls. If you need assistance with these or any other pest, please contact the Lincoln County Extension Office at 706-359-3233 or uge3181@uga.edu.
