For those who may not be familiar with Japanese Beetles, they are native to Japan. However, they are surprisingly not a major insect pest in Japan. Japanese Beetles were accidentally introduced into the US around 1916 in the northeast. The climate and plant diversity that greeted the Japanese Beetles was perfect for their development and expansion. By now, Japanese Beetles, both at the grub and adult stages, are one of the worst insect pests in most states east of the Mississippi River.
Japanese Beetle grubs, which is in the larva stage of the life cycle, feed on the root systems of all cool-season grasses as well as many other lawn weeds and other plants. The adults feed on the leaves and flowers of over 300 plants. Some of the trees that they prefer to feed on include Lindens, Black Walnut, Norway Maples and Flowering Crab-apples. They also feed on garden beans, grape vines and both the leaves and flowers of roses.
The adult Japanese Beetle is easily identified by the tufts of white hairs on the back end of the abdomen. Their wing covers are copper colored and the body is metallic green. The grub stage looks like a typical white grub with a c-shaped body and reddish-colored head.
Each species of grub can be identified, by the pattern of hairs on their raster (the pattern of hairs and spines in front of the anal slit) or anal slit. Japanese Beetles have two rows of hairs that are arranged in a V pattern on their raster.
Females live for about 30 to 45 days and will lay about 40 to 60 eggs. They prefer moist, loamy soil in well-manicured turf in which to lay her eggs. Eggs hatch in about 2 weeks and the tiny larvae begin feeding on fine root hairs and organic matter. By late summer the grubs will be fully grown and can feed on large sections of turf. Turf can easily be pulled up, like a carpet, to expose the grubs.
Japanese Beetle – Control Damage to Your Lawn and Landscape
More damage is often caused to the lawn by the animals that feed on grubs than by the grubs themselves. Grubs are like mini-sod cutters and will feed on anything in front of them – soil, roots and other organic matter. If the lawn is being watered and fertilized, it is sometimes hard to tell if grubs are active. Skunks, raccoons, opossums and even crows will dig up the turf looking for a tasty treat. This will cause more damage to the lawn than the feeding by the grubs.
If you see the adults feeding on your plants, it is a good idea to take steps to control them. The adults usually feed from the top of the tree and move downward. The adults have the ability to defoliate a tree in a short time. Minor populations can be hand-picked and thrown into a bucket of soapy water.
The adults are more lethargic in the early morning and you may be able to shake them into the soapy water. Large populations may require the use of a commercially available insect control material.
One word of caution, female Japanese Beetle adults can fly upwards to a mile, so even if you control the adults in your landscape, there is still a possibility of facing grub damage in your lawn in September. Applying a preventative grub control treatment to your lawn at this time of year is a good idea – especially if you have adults feeding on your plants.
If you have Japanese Beetle adults that are feeding on your garden plants, shrubs or trees, contact your local Spring-Green office and have your landscape evaluated and receive a price to control these destructive insects.