Japanese BeetleJapanese BeetleWhen a horticulturist is asked, “Do we have Pest XYZ here?” many times they will reply, “Well, not yet, but it is only a matter of time.” With that thought in mind, I have been asked for years about the Japanese beetle. Japanese beetles have been defoliating plants in the eastern United States and slowly working their way west.

When I started in Extension a number of years ago, “Not yet, but it’s only a matter of time” has always been my standard reply when asked about Japanese beetles. Well, unfortunately, our time is now up. Japanese beetles have arrived. (I’m told this news was met with gasps when announced at a local rose society meeting, last week)

Over the years, someone would bring in and we would confirm the identification of a Japanese beetle about every couple of years. But this year the Johnson County Extension office has received more samples than I can remember. Professionals in the green industry also report seeing more Japanese beetles than ever before.

Japanese beetles can be troublesome on two fronts. The adults feed on a wide variety of plant materials including: rose, grape, crabapple, linden and birch, to name a few of the more popular targets. The grub can also be a pest of the lawn, feeding on the roots.

What people are finding and bringing into the office is the adult stage, which is active for about six weeks in the summer. The adult is less than ½ inch in length, and metallic green in color with coppery wing covers. The most identifying marking is white tufts of hair that protrude from the end of the abdomen. For the average person, that means white dots on the side of the small beetle. The larvae are a white grub that looks much like the other grubs found in our area. Identification of the Japanese beetle will require a microscope and an up close look at the hair patterns on its butt. (I am going to assume most of you will leave anal inspection to the trained professional. I can hardly wait for your sample!)

Damage by adult beetles is defoliation of the host plant. The good news is many well established plants will be able to tolerate minor feeding with no loss in vigor. The feeding tends to be more in mid to late summer, which means the plant has had more time to store food reserves for next year.

Options for control range from doing nothing to hand removal or chemical sprays. Japanese beetles often feed in clusters, so knocking the adult beetles off into a bucket of water or alcohol with kill them. Chemical sprays such as Sevin or cyfluthrin are effective and will last for up to two weeks. The disadvantage of spraying is the removal of beneficial insects from the plant that can control other pest such as spider mites.

With all that being said, it is not time to panic. Even though we are seeing more Japanese beetles, this is not a widespread outbreak. The purpose of this column is to help you learn how to properly identify Japanese beetles so that if the time ever arises in your backyard, you will be prepared.

So…go ahead and ask me, “Do we have Japanese beetles?” and you will now get a new answer. “Yes. Yes we do,” and from now on it will be in ever increasing numbers. But only time will tell just how damaging their presence might be in Kansas City.

-- Dennis Patton