Answer: There are several Japanese Beetle Control methods available on the market. Whether you intend to blast the beetles with chemicals or go the organic route, you can get control of the dreaded Japanese Beetle. Chemical controls for adults are: Carbaryl (Sevin), Malathion, Permethrin, Bifenthrin, Rotenone, and Methoxychlor. Chemical control for grubs include: Imidacloprid (Merit), Chlorpyrifos, Isofenphos, and Diazinon. June through August is probably the best application time for most Japanese Beetle grub control chemicals as this is when the younger grubs are hatching and feeding.
Organic treatment for Japanese Beetle control can take some time to work or can be a lot of work, depending on the density of your Japanese Beetle population. The simplest organic method is just picking the Japanese Beetles off of your plants as you walk through your garden and pitching them in a bucket of soapy water. Some people like to collect them in a can and feed them to their chickens, should this be an option for you. One note I would like to make here. Japanese Beetles are like little flying solar panels. When they are in the sun, they are very quick to fly away and move from you quickly as you are picking them. Catch them on a cloudy day and they are very slow moving, almost sluggish. Japanese Beetles love Rose of Sharon, especially ones planted in full sun. But if you plant yours where they don't get much sun, then the Japanese Beetles will pretty much not even touch them.
Trapping Japanese Beetles is another option, but the traps seem to draw more and more from neighboring yards. You may also choose to plant plants that are not attractive to the Japanese Beetle.
A form of control for the Japanese Beetle Grub is Milky Spore. It can take several years for this disease to build up and effectively control the feeding beetle grubs, but it does seem to work for a lot of people. Parasitic Nematodes are a new control option available to the home gardener. Some of these products go by the names: Biosafe, Biovector, Exhibit and Scanmask. You'll want to water before and after application of the nematodes.
An important fact to remember is that if you live in an area with heavy infestation of Japanese Beetles, you'll want to try to work with your neighbors in developing a Japanese Beetle control program. This should give you better control of the Japanese Beetle population in your own yard.
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