They're back! Over the weekend, my wife killed about a half dozen Japanese beetles, which means we're at the start of the onslaught. We can hope some of them drowned in our cool wet spring, but I am afraid it only delayed their appearing. I think the University of Missouri Extension actually trapped their first ones June 5 in Boone County.
If you are not familiar with these harmful pests, they are about three-eighths of an inch long and are metallic green with bronze colored wings and white dots (actually little tufts of hair) on the edge of their body. If they weren't so destructive, I would almost think they were kind of pretty. But what they do to the plants is anything but pretty.
They start out as grubs feeding on roots in lawns and pastures or any where else they can find a nice grassy place. The adult Japanese beetles usually emerge the first to middle part June and increase in number for the next four to five weeks before starting to decline. Unofficially, I think they are a little late this year. Unlike some pests that attack only certain plants, Japanese beetles assault the foliage, flowers or fruits of more than 300 different plants.
Keeping the Japanese beetle in control is not easy. The home gardener has several choices. If the infestation is light, hand picking can be done. Japanese beetles are slow and easily picked off and dropped in a container of soapy water. Morning is the best time to accomplish this. Their one defense is to let go and drop off the plant at the first touch so grab quickly. When you pick them off, put them in a solution of 1 tablespoon of liquid dish washing detergent in a 5-gallon bucket of water, which will cause them to drown. Or, you may put put down a dropcloth, and in the early morning when the beetles are most inactive, shake them off onto the cloth and dump them into a bucket of soapy water.
If you are looking for a more powerful method but want to stay organic, you can use a Neem oil product like Azatrol or Neem-Away. Neem oil comes from a tree and discourages feeding by the beetles and a host of other pests. It is most affective when treatment is started at first sight, and it may be necessary to reapply every three to four days. It must be reapplied after rain. Note: Neem can be harmful to fish and other aquatic life, so don't use it near lakes, rivers and ponds.
There are traps made specifically for Japanese beetles, although some say they attract the pests to places where they might not have shown up. The Cole County Extension has trapped up to 3,000 Japanese beetles in one week's time. (One person said the best way to use traps is to buy them and give them to your neighbors.)
If you are inclined to use pesticides, the most widely labeled products and most easily found at local retailers are Spectracide Triazide Insect Killer and Sevin (spray). The former is about a third the price of Sevin for the amount of spray solution it makes. As always, read the label and follow its instructions. Spray insecticides in the evening to reduce the negative effects on bees. Powder insecticides have proven to be more lethal to bees than liquid sprays.
Unfortunately, there is no magic potion to get rid of this pest. Luckily, according to Dean Volenberg, of MU's Grape & Wine Institute, "A natural enemy of Japanese beetles has been established in Missouri: A small wasp,Tiphia vernalis (Hymenoptera tiphiidae), that parasitizes the Japanese Beetle larva. Hopefully biocontrol agents will help reduce Japanese beetle populations."
For general preventive maintenance, experts recommend keeping your landscape healthy. Remove diseased and poorly nourished trees as well as any prematurely ripening or diseased fruits, which can attract Japanese beetles.
The good news is this attack lasts only a month or so. Although that can be long enough for a heavy infestation to do some real damage, light infestations are more common in our area and easier to control.
Happy gardening!
Peter Sutter is a lifelong gardening enthusiast and a participant in the MU Extension's Callaway County Master Gardener Program. Gardening questions can be sent to [email protected]