They’re Back – Understanding and Controlling Japanese Beetles


This is the time of year when the annual onslaught of adult Japanese beetles occurs. These voracious feeders are making leaves look like lace as they feed between the veins. The size of this year’s population is anyone’s guess, but the likelihood that it will be as big as last year is almost a certainty.

Japanese beetles first arrived in the US in the early 20th century and were first reported in New Jersey. They originated in Japan, where they are not considered a major pest. Once they made their way to the US, there were no natural predators and they had an abundance of plant material to feed on. They slowly worked their way west feeding on trees, shrubs, fruit and flowers. Some of their favorite plants to feed on are Lindens, roses, and grapes, but they will feed on many other plants as well.

Japanese Beetles are easily recognizable by their copper-colored wing covers and by the white tufts of hair on their back end. They are the adult stage of an annual white grub. At this time of year, the adults are feeding andmating and the females are laying eggs in lawns. The eggs hatch into grubs about two to three weeks after they are laid. The grubs will feed for about 6 to 8 weeks, feeding on soil, grass roots and other organic material in the soil. In mid to late October, they will dig themselves deep down into the ground where they stay over winter. In the spring, they will rise back up to the upper soil zone, do some light feeding, form a cocoon and pupate back into adults next summer.

Some customers will ask why they still get Japanese beetle adults feeding on their landscape when they have received a grub control application. The reason is that the material we apply for grub control will work on the newly hatched grubs, but not on the adults. The adults have wings and can fly a mile or more in search of food. There are many insect control products that will take care of the adults. You can also contact your neighborhood Spring-Green yard care expert to discuss Japanese beetle control options.