How to Kill Japanese Beetles


Authored by Donna Ryan in Pest Control 
Published on 10-30-2009

Japanese beetles are voracious eaters of foliage while the larvae or grubs of these beetles have an endless appetite when it comes to the roots of plants. The beetles, with no known natural enemies, can cover a territory up to five miles in flight. Initially, the beetle was introduced into the eastern U.S. from Japan. Both the beetle and larvae can destroy lawns, plants, trees and shrubs.

The beetle primarily feeds on plants during the summer months of June and July. The larvae appear in the months of August and September after the beetle lays its eggs in July. After September though, the larvae escape from the top level of the soil where they feed to burrow further down to keep warm during the winter months. They appear again in the early spring before maturing in early summer.

How do you get rid of this problematic insect? There’s a number of ways you can stop the beetle’s infestation of your plants and trees. Probably the safest approach ecologically is to make it a regular habit of picking the beetles from your plants in the early hours of the morning after sunrise and dousing them in a pail of soapy water. Of course, this technique works best when the beetles are not so prevalent.

If the beetle population is a little too massive for you to spend the morning patiently culling the insects off plants and shrubs, then an insecticidal soap may be in order. Put the mix in a spray bottle and apply it to the feasting beetles covering all parts of the plant.

You can also use netting on your plants to divert the beetles’ efforts. Beetles will land on a plant and start feeding on the top. With netting in place, they are unable to get to their food source, so they choose greener pastures and plants on which to feast.

A general consensus of gardeners agrees that Japanese beetles are not overly fond of garlic. You can mix a garlic spray using a pint of water with hot pepper and a couple cloves added to it. Include a drop each of corn oil and mild soap and spray the beetles in the earliest part of the day.

Another way to attack the beetles is to mix one pint of the insecticide pyrethrin with a tablespoon of isopropyl alcohol in a spray bottle. Administer the spray every four days.

You can also keep Japanese beetles at bay organically by planting plants that act as repellants. Japanese beetles have an aversion to rue, tansy, white mums, citronella, larkspur and garlic.

The beetles can also be eradicated with the insecticide sprays of diazinon, sevin, pyrethrum and rotenone.

Just make sure when using any insecticides that you use them when temperatures are lower as high temperatures or heat combined with insecticide can sear or scorch leaves.

Whatever method you use, be just as diligent as the Japanese beetles are in eating your plants.


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