Watch out — this could be a heavy Japanese beetle season

  • Pamela Corle-Bennett
  • Contributing Writer
June 30, 2017
Coneflowers are a favorite food source for Japanese beetle adults. CONTRIBUTED

If you have been in your garden these last few days, chances are you’ve spotted a few Japanese beetles. The adults have hatched, and I have a feeling we are in for a good beetle season.

I am neither an entomologist, nor a prognosticator, nor do I have a crystal ball. However, I have seen quite a few adult Japanese beetles in the last few days and something tells me I might see a lot more in the future. Just a gut feeling and I hope I am wrong.

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The adults have bronze wings with a metallic green head. If you look closely at the adult, you will also see five white hair tufts on each side of the body and two tufts on the rear end.

Adult Japanese beetles have a huge appetite for a wide variety of plants. While many insects are host-specific (i.e. they prefer a certain plant), these beetles feed on more than 300 species of plants.

The saying, “if you plant it they will come” holds true for these critters. If you have their preferred food, they will likely pay you a visit at some point.

Populations of adults have been relatively small in my area (northern Miami Valley) but I heard from readers last year in the Beavercreek and Centerville areas that the populations there were quite heavy.

I really haven’t seen a “bad” year with these adults in quite a while — which is another reason why I suspect I may see more this year.

The larvae or grubs feed on turfgrass roots. There are also other white grubs that feed on turfgrass roots as well such as masked chafer, June beetles, May beetles and the black turfgrass aetanius.

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Again, depending on populations, the larvae can damage a lawn to the point of reseeding or complete replacement if populations are extreme.

Controlling the grub does not lead to controlling the adults. If you have the plants that the adults like, they will come from other lawns. Therefore, controlling grubs should be done if there are enough in the lawn to warrant control.

A few grubs feeding won’t cause a lot of problem for the turf. However, if you find nine to 12 per square foot of turf, you will see lawn damage.

There are several sprays on the market for the adult Japanese beetle. They have to be reapplied every so often (follow the label) in order to keep the adults at bay.

I don’t normally worry about Japanese beetles feeding on trees, but I don’t like them on my roses and hibiscus. I will first knock the beetles off of the flowers into a bucket of soapy water. Once populations become damaging to the flowers, I use pesticide sprays.