Healthy, green grass is a necessity for golf courses, a priority for homeowners, and a delicacy for a little-known invader called the Japanese beetle. Unfortunately for Minnesota, the beetle has made itself at home in the Twin Cities and now appears to be spreading into new parts of the state.

The Japanese beetle was first discovered in Minnesota nearly 10 years ago, but it didn't establish itself as a major pest until recently. According to surveys conducted by the Minnesota Department of Agriculture, the beetle's numbers are increasing and it is proliferating into Winona, Red Wing, Waseca and other areas in southern Minnesota.

With this summer's survey and trapping season three-quarters finished, MDA has already found a 12-fold increase in the number of Japanese beetles collected compared to 1999. In addition, the beetles have shown up for the first time in Wabasha and Goodhue counties.

Unlike some other insect pests such as the gypsy moth, the Japanese beetle causes problems as both a youngster and an adult. In the grub stage, the insect feeds on the roots of grass. It can destroy sizable sections of turf, leaving dead brown patches in its wake. As an adult, the glittering green-and-copper beetle continues to make trouble by eating the leaves of bushes and trees. It is particularly fond of rose bushes and green beans.

To make things worse, the beetles tend to congregate once they find a good home for themselves. That means a lawn or golf course with a minor beetle problem could quickly have a major beetle problem.

MDA Plant Protection Section Manager Geir Friisoe said homeowners and golf course managers can defend their grass by monitoring it for damage. If they notice dead patches of grass that can be rolled up like new sod, it is a possible sign of beetle activity. In the meantime, MDA is taking the offensive against the beetle.

"We use specially scented traps to control severe infestations," Friisoe said. "The intensive trapping program reduces beetle numbers on a small scale, but it would be impractical on a statewide scale. That is why the state is developing natural, biological control methods."

Several biological controls are in the works. For example, scientists are introducing a type of fly and a non-stinging wasp known to be natural enemies of the beetle. In addition, the department is looking at developing traps that would infect the beetle with a fungus that is known to kill it. Before dying, the beetle would carry the fungus back and spread it among other beetles.
Comment Here