It's Japanese Beetle Time Again

by Toni Leland

Oriental Beetle

I saw two Oriental Beetles in the garden this morning, and that means the Japanese Beetles are imminent. After competing with the Gypsy Moth caterpillars for my roses and maple trees, I'm not looking forward to the next battle.

Japanese Beetle

Japanese Beetles (Popillia japonica) are difficult to deal with, and prevention should be combined with physical management. Understanding these insects helps property owners decide how to proceed. University of Connecticut's fact sheet is a good start.

According to UConn, the best time to spread grub control is in mid-July; this will kill the newly-hatched grubs in August as they begin to feed on the roots of turf grass. Many folks use grub control in the spring, but the documentation says that it is less effective due to the depth of the maturing grubs. Homeowners will need to read the literature to formulate a decision.

Physical management is the only thing that has worked for me in the past few years. Knowing which plants and shrubs on my property are magnets for these beasts gives me a plan of attack. As mentioned above, when the Oriental Beetles (Anomala orientalis) emerge, I start watching for the first Japanese Beetle.

In the past, I've had success with draping gauze over my roses and ornamental laceleaf maples. The beetles emerge from the ground and fly around, looking for food. They do not crawl up into shrubs, therefore the gauze is a good foil. Of course, this is not feasible for mature trees.

For plants such as daylilies and other attractions, my morning routine is a stroll around the gardens, hand-picking the beetles into a container of soapy water. It's tedious, but it works!

Sometime in early August, I'll start seeing these adult beetles with tiny white spots on the back of their heads. These beetles have been parasitized by tachinid flies. This natural predator is welcome in my garden anytime, and when I come across a beetle that has been used as a fly nursery, I leave it alone. All those white spots will hatch into more tachinid flies and the cycle continues.

Isn't Nature grand?

Read on for more than you probably ever wanted to know!