Pesky Pest: Japanese Beetles

     Japanese beetles, Popillia japonica, are probably the most frequent pest insect to harm our gardens and landscapes. Native to Japan they were first discovered in 1916 and were suspected to have hitched a ride in a shipment of iris tubers that arrived at a nursery in New Jersey. Since then, they have gone on to establish themselves in nearly all of the eastern United States as far west as Arkansas and north to Ontario Canada.  They are about a half inch long and have a greenish to brownish metallic sheen.

     Japanese beetles are not a problem in their native Japan because of natural enemies that keep their populations down, but here in the US that’s not the case. Here they tend to gather in large numbers and decimate plants. (see photo below, taken by D. Gordon E. Robertson). They eat the tender parts of the leaves between the veins so that they’re ‘skeletonized’. They love roses, filberts, Japanese maples, sycamores, and many, many other plants. They do tend to avoid evergreens, I guess the leaves aren’t as tender.

     Well, how do you get rid of them?  One form of control we’ve seen for years is that bag trap thing you hang in your yard with the pheromone/scent lure. Well, research has shown that yes they do attract beetles very well, but unfortunately, they do not trap that many. The beetles are attracted to your trap and eat your plants on their way to the trap and they eat them as they hang around not being trapped in the trap… So hanging one in your yard will actually cause more damage to your plants than not having one at all. So maybe sneak one in the yard of that mean guy down the street… (kidding!) Seriously though, there are many different chemicals to control Japanese beetle populations out there. Despite this they are still hard to control. You have to apply a chemical to your turfgrass in early spring to kill the grubs, and then you have to spray for adults repeatedly through the summer because they are so mobile they can come to your yard from anywhere. So to me, that sounds like an awful lot of chemicals that aren’t that effective. One old school way to kill them that works for small infestations or small yards is soapy water. You can just knock them off the plants early in the morning when they’re sluggish and drop them in soapy water.  Sraying soapy water is somewhat effective as well.

     Now the best Japanese beetle control, according to our esteemed Mr. Bishop is to make margaritas. His advice is to take the down-the-street-neighbor’s full trap, dump it in your blender, add some water and spray this delightful concoction on your plants. And of course, don’t use that blender again for actual margaritas. Having never done this myself, I can only say that research has shown that live beetles avoid dead of their own kind.

So, good luck!

Jessica Watters, GCLP Horticulture Technician, Chattahoochee Technical College