How to Control Japanese Beetle Grubs

Japanese Beetles are destructive pests that thrive on plants and flowers, especially roses. You can try to control the beetles with insecticide, but that is almost a daily challenge. The real culprit is the grub, which is hatched from Japanese Beetle eggs. To control Japanese Beetle grubs, you first need to understand the cycle of the beetle. Once you know the cycle of the beetle, you can control the grub by fighting both the beetle and the grub. Then you can save your precious landscape from the destruction of this annoying pest that can turn thriving plants into skeletons.

Soapy water

insecticide

Milky spore powder

Learn the cycle of the Japanese Beetle. Adult beetles emerge from the ground in early June. They live for 30 to 45 days in which time they can destroy the landscape by feeding on plants. During the feeding, the female beetle will leave periodically to lay eggs in the soil. In midsummer, the eggs will hatch into the larval stage (grub) and the grubs will begin to feed off from the soil. In late fall, the grub will burrow down into the soil deeper where it will remain inactive for the winter. In June, the cycle begins again with the adult beetle emerging from the ground.

Eliminate the beetles present on the plants. During the 30 to 45 days in which the beetles are feeding, begin eliminating as many as you can. This is a process that must be repeated continuously throughout the summer months. They will travel up to five miles, so even though you eliminate the beetle from your yard, you will continue to have beetles flying in from other locations. This isn't meant to be discouraging because eventually, you can control the beetle. There are two ways to alleviate the adult beetle.You can pick them off daily and place them in soapy water where they will die. Pick them off the plants in the early morning when they are sluggish or shake the plants and pick them off the ground. Spray the bugs with insecticide that is specific for Japanese beetles. Spray often because of rain and the continuous flying in of other beetles.

Eliminate the grubs in the ground. The use of Milky Spore powder will effectively kill the grubs. Milky Spore can be bought at most garden centers. This powder is not harmful to man, birds, or any beneficial insect. The powder enters the ground where the grubs will ingest it. The grubs die and leave more spores for more grubs to ingest. One application of the powder in the fall when the ground is still warm and the grubs are eating, should take care of the lawn for up to 20 years. You can apply the spore again in the spring, but two applications should be enough.

Follow the directions for the Milky Spore. Directions will vary for different products, but usually the process is similar. One teaspoon on the top of the grass every 4 feet in rows of 4 feet apart is all that is needed. Then the ground needs to be watered. It takes about one pound of Milky Spore for 4,000 square feet.

Continue eliminating the beetle. When June arrives the following year, continue to eliminate the beetle by picking it off plants or using an insecticide. You should not have to use the Milky Spore again for the grubs. It will take a few years to finally control the population. If you have neighbors who will join in with the effort, it certainly will help since these pests fly up to a five mile radius.

Plants that Japanese beetles do not like are boxwood, red and silver maple trees, flowering dogwood, rhododendron, lilac, holly and red oak. There are others as well.