Summer is here and so are the Japanese Beetles. These metallic green and copper beetles love our roses, grapes, basil, green beans and even chew a bit on our Crapemyrtles. Drat!
It is shown that the presence of Japanese Beetles will draw more of their friends so if you can get out there into the garden as soon as you see them and reduce the population immediately, their friends will be less likely to follow.
The best method of control of these adult beetles is to quietly sneak up on the beetles with a wide-mouthed jar of soapy water and knock them into the water for their final swim. In most cases beetles will drop before they fly. Remember the more you catch early on, the fewer you will have later. The early morning is a great time for capture.
Most insecticides on the retail market are broad-spectrum and so will also be toxic to our valued bugs such as bees, ladybugs and other predator bugs. Systemic insecticides, which can be effective on beetles, are also damaging to bees. Neem oil is a possibility since it is not used as a knock-down of the bugs, so to speak, but coats the plant leaves on which the Japanese Beetles feed. On ingestion, the Neem oil does its damage. Bees do not eat the leaves, as beetles do, but go for the flower nectar instead. Neem oil can have some repellant effect for a minimum of time. With Neem or other sprays do not apply when bees are present on the plants.
Pheromone traps can capture some of the population but can also attract the beetle to your garden. Post the traps at least 30 feet away from plants you want to protect. Some folks rig the trap to funnel it over a bucket of soapy water, allowing for greater capture.
It has been known for some intrepid gardeners to go out into the rose garden with a shop-vac and suck the bugs into their doom.
In general, the most effective method of control of adult Japanese Beetles on your plants is hand-picking or dropping in soapy water. Happy hunting!