Japanese Beetles


In my travels around the county I have noticed already several Japanese beetles. This may be a sign of a bad infestation this year. Japanese beetles were introduced into this country in the early part of this century and have now become well established in the Eastern United States. Both adults and larvae cause damage to landscape plants. The adults have a very wide host range meaning they will feed on many different types of plants. Some reports indicate that the adults will feed on up to 300 different species, even poison ivy! The larvae or grubs are more selective and feed on the roots of grass species. This root feeding produces the grass’s ability to take up water resulting in the grass being more susceptible to the hot dry conditions typical of summer. Heavy infestations that are not controlled may result in large patches of dead grass. Birds and moles may also cause damage to lawns as they dig and extract grubs from the soil.

Adults emerge from the ground and begin feeding on plants in June. Activity is most intense over a four to six week period beginning in late June. Adult beetles live almost 30 to 45 days. Egg laying begins soon after the adults emerge from the ground and mate. Females leave plants in the afternoon, burrow two to four inches into the soil in a suitable area and lay their eggs. The developing beetles spend the next 10 months in the soil as white grubs.

So, what is to be done about these pesky insects? There are several approaches one may take in attempting to control these insects. Physical control measures (manually removing beetles from plants) should be implemented as soon as possible once beetles appear, since the presence of a few beetles on a plant tends to attract more beetles to the same plant. If infestations are relatively light, the beetles can be removed by hand or shaken off the plant. The best time to remove Japanese beetles in this manner is in the cool of the morning when the insects are less active. Once the beetles have been collected, they can be killed by placing them in a bucket of soapy water. Another way to control Japanese beetles is aimed at controlling the larval stage, the grubs. Insecticides (sold under various trade names) can be applied to turf but this approach has been met with mixed success. Even if the treatment does control grubs in turf, which in and of itself is important, there is nothing to prevent beetles from flying in from neighboring yards to infest your ornamentals. Adult Japanese beetles are extremely mobile and can infest new areas as far away as five miles. Another approach has been the use of Japanese beetles attractants that lure the insects to traps where they are captured. Unfortunately, these attractants work too well and often attract more insects than are captured. If you prefer to use insecticides, several are effective against Japanese beetles. Products containing Sevin® are quite effective, and can be used by homeowners. Remember, always read and follow the label directions that come with an insecticide. If the label does not list Japanese beetles for the crop or plant you are wanting to spray, do not use it.

More information on aquaculture topics is available at the Meade County Extension Office.

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