Look out into your yard. Do any of your trees have a neon sign flashing “Food Food Food--The Place to Eat!”? Most people did not plant their trees to create a fast food station for insects. Could someone please tell this to the voracious Japanese beetle?

Native to Japan, as the name suggests, this beetle is a huge pest in the eastern USA and unfortunately, it is moving west. The adult is oblong with metallic green coloration. The larva or grub lives in the soil and feed on roots.

Japanese beetles are chewers, and they can chew alone or in a crowd.  Together they can chew their way along and completely defoliate a tree or shrub in short order. Japanese beetles feed on the foliage or flowers of more than 300 species of plants, including fruits, vegetables, ornamentals, field and forage crops, and weeds.  Norway and Japanese maples, birch, crabapples, purple-leaf plums, roses, sassafras, mountain ash and linden are highly preferred ornamental hosts. 

How do you manage Japanese beetles? They do have a few natural predators (predatory wasps), but these predators are not as effective with the Japanese beetle as other beneficial insects are with aphids, mealy bugs, etc. If you see only one or two, you can hand pick them and squish, drown or flush.

When there are only a few Japanese beetles on a tree or shrub, handpicking removal is actually effective. The beetle is releasing pheromones that will attract masses of Japanese beetles; collecting up the few that you observe, and even hosing down the plant, will help stave off the arrival of more adult beetles.

But if you have a tree teeming with them, there are a few treatments to try. One is a yellow target trap that is treated with a lure to attract the beetle. These traps are effective, too, (for the same reason hand-picking collection works) when numbers of pests are low.

The grubs, larvae of the beetle, can be killed by introducing parasitic nematodes. Or there are other pesticides available that will target the larvae. Don’t hesitate to consult with one of our salespeople.

If the infestation is large, there are pesticide sprays. Please be sure to ask one of our salespeople which product would be best suited for your problem. Japanese beetles love fruiting plants, and you must be careful which product to apply if the fruits are intended for consumption.

For a more detailed listing of control recommendations, visit http://learningstore.uwex.edu/pdf/A3737.PDF where an article by R. Chris Williamson, a turf and ornamental specialist in the Department of Entomology at the University of Wisconsin-Madison and University of Wisconsin-Extension, Cooperative Extension, is available for review.