Japanese Beetles Do Double The Damage

Japanese Beetles are one of the most hated and damaging insects to gardens and lawns. Controlling them takes a multi-pronged attack but is possible. The key, is understanding their life cycle.

Japanese Beetle Life Cycle

Japanese Beetles actually start out as white grubs in the ground below your lawn and garden. The female adult lays its eggs in the ground in July. The grub hatches and begins eating roots until late September when it starts getting colder. At this point, the grub burrows deeper into the ground to rest for the winter. When spring comes, the grub comes back near the surface and feeds on roots again. In June, the grub pupates and emerges as an adult to feed on your favorite garden plants (we’ll get to that in a minute).

Recognizing Japanese Beetles

The adult of the Japanese Beetle is actually quite pretty. At about 3/8” in size, it has an out shell that is coppery in color with a green head. The grub is a little less than an inch long, white in color with a dark head, and resembles the letter “C”.

What Do Japanese Beetles Eat?

If you are reading this post, you are probably already experiencing the damage to your garden.

While they will feed on numerous plant species the adult Japanese Beetle prefers roses, roses, birch, elms, Japanese maple, crape myrtle, linden, raspberries, and grapes.

The grub will feed on grass roots as well as roots of corn, beans, tomatoes, and strawberries.

Japanese Beetle Damage

This is actually quite easy. The adult eats leaves in a way the “skeletonizes” them meaning, they eat the flat part of the leaves but not the veins of the leaves. The beetles tend to feed in groups and will work their way down from the top of a plant. They are most active on warm, sunny days and prefer plants in sunlight.

In the lawn, recognizing grub damage is also quite easy and obvious. The first sign is to look for new brown areas in your lawn. If grubs are active, the brown areas can actually be rolled up like carpeting. In most cases, the white grubs will be visible just under the surface. Another sign to look for is birds, racoons or skunks digging after the grubs.

Controlling Japanese Beetles

An important point to remember is that eradication of the adult Japanese Beetle is impossible. The adult can fly from very far away to feed off a desirable plant. If there are only a small amount of adults present, simply picking them off and sticking them in a cup of water mixed with dish soap is adequate. There are numerous insecticides available to treat adult Japanese beetles as well. Japanese Beetle traps baited with pheromones are touted as a solution but many feel the actually draw more beetles to the area. If used, the should be located 20 -30 feet away from the at-risk plants.

Timing applications is the key to controlling Japanese Beetle grubs. Applications must be applied when the grubs are near the surface. There are numerous pesticides available for this as well as non-pesticides materials such as neem oil and milk spore.

If choosing a pesticide option, consult the product label and your local extension service for safe application processes.


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