When one of these beetles finds a tasty plant, they send out signals through pheromones to all of their buddies. Their buddies come and almost overnight the rose blossoms on your favorite rose, or all the leaves on your grape vine or birch tree, are gone.
When you see these greenish colored beetles with bronze backs outlined with white tufts devouring your favorite garden plant, you can easily kill them by spraying spinosad, malathion, permethrin, sevin or any other insecticide that kills when ingested. The problem is that the beetles keep coming. So you may need to spray more than just once.
You can keep these beetles from devouring your garden if you place beetle traps in prime locations around your garden. But make sure you place enough traps around your garden to lure all of the local Japanese beetle population into the traps. One trap in your landscape will attract the whole neighborhood's population. But if this trap is not large enough, many beetles will come to the trap, not be captured, and then move on to dine on the tastiest plants in your landscape.
Japanese beetles are going to be more and more of a problem in the future. If you are seeing these beetles in your landscape now, rest assured you will also find them next year. Right now the adults are feeding, mating and laying eggs in soil around your garden.
These eggs will hatch in a few weeks and the resulting grubs will eat plant roots in your lawn and your landscape the rest of the summer into the fall. The adults hatch in the spring and they start the cycle all over again. If the grub infestation is high enough, the resulting damage can show up as the demise of your favorite landscape plant or large brown patches in your lawn that you can pull back like old carpet.
So if you have seen Japanese beetles in your landscape this summer, I recommend you apply imidacloprid to your lawn in August. By this time, most of the adults have laid their eggs. A timely application should control most of the grub population.
Another product, milky spore disease, is a granular form of bacteria (Bacillus popilliae) that kills the grub of Japanese beetles. A total of six applications done in spring, summer and fall are recommended over a two-year period. This bacterium will establish itself in the soil and should last several years. Unfortunately it only seems to work on Japanese beetle grubs. If you have also been seeing infestations of June bugs, use the imidacloprid product.
Japanese beetles will be a problem in the years to come. The proper use of pesticides and traps will keep the population in check, but without constant vigilance and the appropriate response, they can cause considerable damage to your landscape. Good luck.
Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, Mo. 63702-0699 or by e-mail to email@example.com.