Japanese Beetle - Popillia japonica

A Little Bug With a Big Appetite!

Last year was a particularly tough year for gardeners in the Finger Lakes region of New York as they battled the hordes of Japanese Beetles, myself included. By mid-July, it seemed like these little guys were everywhere and they had VORACIOUS appetites! 

Popillia japonica was first discovered in New Jersey in 1916. A native to Japan, it found both an abundant food source and a favorable climate in the United States along with few natural enemies. As of 2007, the Japanese Beetle population has spread westward to nearly half of the United States. As seen in the above photograph, a Japanese beetle is about one-half inch long and has a green metallic body with coppery-bronze outer wings.

Japanese Beetles are the ultimate garden destroyers as far as pests go. As grubs or larva, they eat the root systems of plants and grasses. As adults, they feed on the leaves and fruit of a myriad of plants from ornamental trees and shrubs to fruit and vegetable crops. They are truly eating machines! 

The Japanese Beetles in my area went right for the Cherry trees (both ornamental and fruit-bearing). Second choice seemed to be the grape vines, followed by my rose bushes and finally, my strawberries. The Cherry trees were left with mere skeletons where leaves had been only a few days before. The other plants had many holes in the leaves, but at least there was some greenery left.  Thankfully, my trees seem to have survived and recovered just fine - likely just in time for another round!

Japanese Beetles can be controlled by using chemical methods, biological methods such a nematodes or parasites, or mechanical methods such as the Japanese Beetle Trap. I have only used the trap myself, as I personally prefer to steer clear of most chemical methods. I can honestly say that the traps work very well (and will literally catch hundreds of Japanese Beetles in a single trap), but as they work by attracting adult beetles make sure that you place the traps at the very edge of your property away from any tasty plants.

The USDA has an excellent PDF document called Managing the Japanese Beetle: A Homeowner's Handbook. It provides a list of plants which are susceptible to the Japanese Beetle as well as a list of plants which are not and may therefore be a better choice for your landscaping plans if Japanese Beetles are present in your area. This informative booklet also explains different control methods and how they work, so that you can decide on the method that is best for your particular circumstances.

As the Japanese Beetle is apparently here to stay, it is our responsibility to find an effective and environmentally safe method for minimizing the damage caused by these little critters. To this end, I wish you the best of luck and a beetle-free summer!

Please refer to our Gardeners' Potpourri Archive for additonal articles.