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Are your plants glinting in the summer sun? Starting mid-June, Indiana residents should keep an eye out for a shiny, metallic beetle with a green head and copper wings. These are likely Japanese beetles and they eat the leaves of shrubs and trees.
Leaves affected by the Japanese Beetle have a lacy appearance and can be completely skeletonized; flowers may be chewed as well. Favorite plants of the beetles include Roses, Hibiscus, Rose of Sharon, Japanese Maples, Tilia species (Basswoods, Lindens) etc. Generally, they are not attracted to Boxwoods, Hydrangeas, Lilacs, Clematis, Daylilies, Oaks, or Yews. Generally, this is a cosmetic issue and should not kill your plants.
Control of Japanese beetles will vary depending on the level of infestation. When very few are seen, an easy solution is knocking them into buckets of soapy water to kill. Some gardeners use Neem oil as a repellant if it is sprayed before the beetles have begun to feed on plants, but it is not effective enough to garner endorsement from tree and shrub care specialists. Japanese Beetle traps are not recommended as they may attract more beetles rather than discourage them. There is no preventative spray for the beetles, only a contact insecticide.
Some of the products we carry include:
Eight Insect Control Yard & Garden can be used to treat the grubs in the turf or plants that the beetles are feeding on. We have it in an RTU (ready to use hand spray without any mixing) and an RTS (ready to spray: hooks up to a garden hose). The main chemical ingredient in Eight is Permethrin. Eight should be sprayed in June/July, every 10 days, although it may be used less frequently for other insects. Avoid spraying the flower blooms themselves as it is toxic to bees.
Sevin can be used to treat adult beetles, but is only effective if it comes in direct contact with the beetles. The main chemical ingredient in Sevin is Carbayl; avoid spraying when bees are active, as it is toxic to bees. Repeat applications can be made every seven days.
All in One Rose & Flower Care by Bio Advanced helps to control adult Japanese Beetles on Roses and other flowering shrubs and perennials. It should be applied every six weeks, as it also helps to prevent other insects and diseases, and fertilize as well. It is available in a concentrated formula to be mixed in water and poured on roots. Avoid contact with foliage and blooms, as it will affect bees and other pollinators.
As always, be sure to read the entire chemical label for directions as well as safety precautions. Avoid direct contact with skin or eyes. Generally, keep pets and humans out of the application area for the specified time on the label.
Wasson Nursery offers infestation treatment through our Lawn Care department. Typically, Japanese Beetles are only present for a few weeks, however, in the past they have been an issue for more than a month and a few customers had to get multiple treatments. Because of this we cannot guarantee that one spray will eradicate the pests. To schedule a Tree and Shrub appointment or for more information, visit our Tree and Shrub care page here.