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Eastern gardeners are all too familiar with how these beetles skeletonize leaves and demolish plants, especially roses and grapes. The larvae are white grubs that feed on organic matter and roots of grasses in the soil; they can cause a great deal of damage to your lawn.
What to do now: Pick off or knock the beetles from plants into a bucket of soapy water. Don't bother to invest in those beetle bag traps: They tend to attract more beetles to your yard than otherwise would have been there. Parasitic nematodes (Heterorhabditis spp.) prey on the grubs, says David Shetlar, Ph.D., extension entomologist at Ohio State University. (He does not recommend milky disease spore products, which are often used to control grubs in lawns.) Apply nematodes to the soil in late August or early September, Dr. Shetlar advises, and make sure that the nematode product is fresh and the soil is kept continuously moist after it is applied.
Next year: Cover garden vegetables with floating row covers by mid-June to keep the beetles off, or spray fruit and vegetable plants with kaolin clay (sold as Surround). And let your lawn go dormant in summer, Dr. Shetlar urges. Watering to keep the lawn green, he says, "is just begging for white grub problems!"
