Controlling Japanese Beetles
You won't be able to eliminate Japanese beetles forever. Instead, the trick is to learn how to manage them.
While Japanese beetles can fly in from as far away as five miles away, it is more likely any that show up in your lawn are coming from a closer distance. In either case, whatever you do on your own property is but a temporary solution to a much bigger issue.
Through a process called Integrated Pest Management (IPM), the following are some methods to control adult beetles, starting with the least environmental impact method. So, with the spirit of IPM as our guide, here are the most common approaches.
Hand picking is easy and very effective when populations of beetles are small. Just take a jar or bucket of soapy water in hand during an early morning stroll in the garden and simply knock the pests into the container. They won't be coming back out. This daily exercise can be very productive.
Trapping involves those yellow Japanese beetle traps found at home-improvement stores and garden centers and seen in many yards and gardens. These work very well at attracting the beetles to the traps. But, the problem is they work too well. Study after study shows they attract far more beetles than they catch. Consequently, they can actually draw more beetles to your yard than if you didn't use the traps at all.
Chemical insecticides are available that kill adult beetles (and many other insects as well). Two of the more common choices include carbaryl, found in the product Sevin, and acephate, found in Orthene. Active ingredients such as these can be found in many different product names. I've just listed two of the most common.
Unfortunately, chemical controls such as these are non-selective. A chemical is very effective in controlling pests but can kill just about any insect that comes in contact with it, including beneficials and pollinators. If you resort to these control measures, please exercise appropriate care. Be sure to apply late in the day or evening and when winds are calm to minimize the adverse impact.
A more "selective" control method against adult Japanese beetles is a systemic insecticide named imidacloprid. This active ingredient is sold under various product names, including Bayer Advanced Tree and Shrub Insect Control. This product is applied to the soil as a drench, and it is taken up through the roots. The active ingredient is not transmitted to an insect until foliage is penetrated or consumed. In this way, non-pest insects such as lady beetles and honeybees are not harmed.