I was golfing with my daughter last week and ran into a few old friends. No, they weren't riding in the cart or hiking around the course. They could fly easily from hole to hole. It seems like we ran into each other around every turn. I stopped counting after colliding with a dozen of them. These old friends aren't actually old, but they are what you would call mature. Mature Japanese beetles.
When you see the beetles flying around, you know it is time to protect your lawn from the larvae they will plant. Their babies start out as grubs and like to feast on your lawn.
Ohio State University entomologists rate them as the most abundant landscape pest in the region. The beetles eat leaves and flowers. Their babies feed on the roots in your lawn.
Those metallic green bugs start to emerge in June and July. The female will lay up to 60 eggs in just a few weeks. By the middle of August, most of the eggs are laid and will hatch about two weeks later.
Once the larvae emerge, they are also very hungry and will start munching on the roots in your lawn. They dig deeper into the soil during the winter and come up in April again ready for a feast. Some people have luck hand-picking the grubs out of the soil.
Scientists don't usually recommend using pheromone traps unless you are getting the entire neighborhood to use them. Those yellow bags call in bugs from many yards away, so you want to keep the traps as far away from your garden as possible.
Controlling the grub population before they move in will give you a jump on next year. Biological controls such as bacterial milky disease will make the grubs sick. But scientists say you need to apply it for two to three years before the spore count in your yard is high enough to be effective. Other biological controls, like parasitic nematodes, are available. Some tests indicate they are only marginally effective on white grubs in turf. Tests show that products containing Heterorhabditis spp. seem to work better.
The most effective chemical control comes from products like imidacloprid, also known as Merit ad halofenozide, usually labeled Mach2. These drugs act like diet pills for grubs, and the larvae end up starving themselves.
One way to keep Japanese beetles from flying into your yard is to plant things that the adults don't like. Scientists say they won't feed on such plants as arborvitae, baby's breath, begonia, bleeding heart, boxwood, caladium, Chinese lantern plant, columbine, coral bells, coreopsis, cornflower, daisies, dogwood (flowering), dusty-miller, and euonymus. They will also avoid false cypresses, firs, forsythia, foxglove, hemlock, hollies, hydrangeas, junipers, kale (ornamental), lilacs, lilies, magnolia, nasturtium, poppies, snapdragon, sweet pea, sweet-William, violets and pansy, or yews (taxus).
Trying to rid your lawn of grubs between September and April is tough. By then, scientists say, the grubs have stopped eating. You could always try a treatment of trichlofon and carbaryl, such as Sevin. Water your lawn well to make sure you get the chemical into the soil.