Meet the beetles! Get to know Japan's voracious insect

Over the past several years, gardeners have told me that Japanese beetles were attacking their landscape.

When I looked at the landscape, or looked at samples of beetles that were brought to me, I identified, not Japanese beetles, but our common June bugs or May beetles.

I have often been asked where to get milky spore disease powder because the gardener was sure that they had Japanese beetle in their landscape. Milky spore disease is known to kill Japanese beetle grubs. Again after seeing samples of the "Japanese beetle", I found only grubs and adults of the common June bug.

Japanese beetle is an insect that was imported into New York State from Japan around 1915. Since that time the population exploded and began to spread westward. Indiana and Tennessee were known to have populations of this insect. In fact, nursery stock sent out of these and other eastern states had to be treated in order to prevent the spread of this insect.

Again this spring I heard reports of Japanese beetle near Cape Girardeau. I can tell you now, with certainty, that this voracious plant eater has made the Heartland its new home. I have seen samples brought in from Scott City and Brewer, Mo.

Japanese beetle adults emerge from the soil around May or June. These adults can be easily identified because they are about a half inch long, metallic green, and have five tufts of white along the outside of each hard wing on its back. The white tufts are the distinguishing characteristic.

When an adult finds a favorable plant to munch on, it emits a congregational pheremone. This scent tells other adults it has found a plant that tastes very good. So other adults congregate on this host plant and strip it of all foliage within a few days to hours. All that is left of the plant are the stems and leaf veins.

The adults of our native beetles, such as June bugs also eat plant foliage, but they do not emit a congregational pheremone. Therefore an entire plant is usually not stripped in just a few days.

In addition, when a female Japanese beetle adult emerges from the soil, she emits a pheremone so that adult males may find her. After mating she lays about 20 to 40 eggs in the soil. These eggs change into C-shaped grubs that live in the soil until the following spring.

These grubs feed on plant roots. If the concentration of the grubs in the soil is high enough, (I have seen upwards of 10 to 20 per square foot) turf can be destroyed as well as flowers and shrubs.

There are two times during the year when you should try to control Japanese beetle populations in your landscape. In May or June when you find adults eating foliage in your landscape, spray the affected plants with permethrin.

Keep in mind that permethrin does not have a long residual, and that Japanese beetle adults are very mobile. Therefore if you kill all of the Japanese beetles that are attacking your shrubs on any given day, you may find a new infestation in a week or two. You will have to repeat your application of permethrin.

If you find adult Japanese beetles in your landscape, then you should also treat the soil of your lawn and landscape beds in August with halofenozide. This product will kill grubs in the soil.

There has been a lot of publicity about milky spore disease over the years. Tons of this bacterial product has been sold as a control for Japanese beetle grubs. My entomology buddies tell me that they are not sure that milky spore gives good control. If you do use milky spore disease as a control, be sure to see if it is doing the job about a week after application.

I wish that I could still say that the Japanese beetle has not made it into Southeast Missouri. But the current outbreaks tell me that the beetle is here to stay. Your best protection is to periodically inspect your landscape plants and make applications if needed.

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, Mo. 63702-0699 or by e-mail to news@semissourian.com.