I have received several reports of high populations of Japanese beetles in localized areas. The Japanese beetle is a shiny, coppery, green-headed insect that grows to about one half an inch in length. This pest is one of the most devastating to our landscapes and gardens. This insect is a defoliator, leaving the leaf lacelike or skeletonized in appearance or completely eating the entire leaf.
The Japanese beetle is both a pest as an adult and as a larva. As soon as the adults appear in spring, they begin to mate and lay eggs. Once the eggs hatch, they live underground for the next ten months as white grubs. These grubs can wreak havoc on lawns, as well as attract wildlife such as skunks and moles that eat them. Once they emerge as adults, they feed for 4-6 weeks.
So what can you do to battle this insect? Start by selecting the right plant. Some plants are preferred by these beetles over others. Landscape plants especially prone to damage include roses, grapes, Japanese maple and purple leaf plums. Plants that seldom see damage include dogwood, lilac, and magnolia. For a more complete listing of plants that are recommended go to https://entomology.ca.uky.edu/ef451.
Remove the insect from the plant when you see it and dump it in soapy water. Try this in the morning by shaking the plant and knocking of the insects. Insects tend to be sluggish in the morning while it is still cool. This works especially well when numbers are low. If you allow them to stay on your plants, it will only attract more beetles.
There are many insecticides available to use against Japanese Beetles. For more information on those chemicals, checkout this publication listed above. There is also a new chemical called Spinosad which has been shown to be effective. When using any treatment against insects, be sure to get good spray coverage. Make sure to cover both tops and bottoms of leaves, as well as the flowers. As with any chemical, read the label for details on how to apply safely. These insecticides will kill other insects, so be aware of when and where you are spraying to avoid affecting pollinators.
Research has shown that the Japanese beetle traps actually attract more beetles than they catch, ultimately doing more harm than good.
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