Dr. Grow: Japanese beetle draws sudden interest in area

I recently have been asked more questions about the Japanese beetle than I have during the last 20 years. Several people have suggested that the demise of a plant in their landscape might be due to an attack by the Japanese beetle. A few people wanted to know how to protect their landscape from impending onslaught. I'm not sure why the sudden interest.

Over the years, I have had several discussions about Japanese beetle with my friend Larry, an entomologist. I thought I would share the information gleaned from these discussions as well as information published in a USDA handbook entitled "Managing the Japanese Beetle:A Homeowners Handbook."

The adult Japanese beetle is a half-inch long and has a metallic green body with bronze-colored wings. Visible along the edges of the wings are small tufts of white hair. The adult is primarily found during late spring and early summer.

The adult feeds on foliage of favored landscape plants. The feeding female adult will occasionally quit feeding, burrow 3 inches into the ground, generally in an area covered with grass, and lay a few eggs. She then returns to plant foliage and continues to feed. She will repeat this feeding and egg-laying cycle until 50 to 60 eggs are deposited. She will eventually die.

The egg hatches in midsummer, and the resulting young grub begins to feed on plant roots. The C-shaped white grub with a brown head continues feeding until late autumn. At that time the grub burrows into the ground to a depth of 4 to 8 inches, where it remains inactive during winter.

In early spring the grub returns to the soil surface and again feeds on plant roots. During April or May the grub changes into a pupa. About two weeks later, the pupa changes into an adult, and the cycle begins again.

Why does everyone seem to be concerned about the Japanese beetle? To answer this question I'll have to give you a very short and oversimplified course in ecology. The population of any organism is controlled in a natural setting by its environment and by competition between other members of the population and between other organisms.

Let's consider a hypothetical population of an insect I'll call Bug-me. The overwintering larvae of Bug-me will survive if the temperature does not drop below 10 degrees F for five consecutive days. If the temperature drops below that threshold level, then 50 percent of the population will die. This would be an example of environmental control of the population.

Suppose another insect, Bug-eater, is a predator on Bug-me. When the population of Bug-eater gets large enough, it will effectively control the population of Bug-me through predation. This would be an example of one organism being controlled by another organism.

Finally if Bug-me feeds on only one particular plant named Bug-food, the insect population will continue to grow until all Bug-food plants are gone. When Bug-me runs out of food, most of the individuals will die, and the population will be controlled by competition within the same organism.

The population of the Japanese beetle, a native to Japan, is under control in its natural environment because of competition with other natural organisms. However, it was introduced into the United States nearly 80 years ago. The beetle, now out of its natural range, has very little competition from other organisms. It also feeds on a wide range of plant material, and thus, it's population isn't controlled by a lack of food. The population of the Japanese beetle is increasing and spreading seemingly unabated.

The outbreak of the Japanese beetle is devastating because of several factors. First, the adult feeds on a wide range of landscape plants. Second, the larvae eat grass roots and destroy sod. Last, because there are very few effective controls on the population, it is increasing rapidly. With so many mouths to feed, it is no wonder the Japanese beetle can cause so much damage.

The Japanese beetle is found east of the Mississippi River in the United States, and there are a few small populations in St. Louis, Springfield, Kansas City and Wichita, Kan. Entomologists do not think there is a breeding population in the Heartland, although an occasional insect is found in this area.

I would tell you how to attempt to control the Japanese beetle, but because there is no population in the Heartland, there is no need for control. Unfortunately I think it is just a matter of time until the beetle takes up residence here. Until that time, rest easy and thank your lucky stars.