Native to Japan and an accidental introduction into the United States in the beginning of the 20th Century, Japanese beetles (Popilla japonica) are now wide-spread in the eastern United States and becoming more widespread in the Midwest. With no natural predators in this country, they enjoy virtual free-rein in landscapes and gardens and can completely defoliate rose bushes and linden trees, two of their favorites. Natural controls can help to reduce populations of Japanese beetles to a manageable level.
Plant Marigolds, Nasturtium and Chives
Japanese beetles are picky about the crops they eat. The scents of marigolds, nasturtium and chives have been shown to repel Japanese beetles. They will avoid areas containing these plants and move on to feed elsewhere. Completely surround affected plants with these deterrents on which you notice the most Japanese beetles. For plants that are slightly less attractive to these beetles, plant one or two of the deterrent plants near them.
Minimize Lawn Area
Female Japanese beetles prefer to lay their eggs in well cared for lawns. Studies on commercial blueberry fields by Michigan State University have shown that growing a cover crop, such as clover, between rows of blueberries reduces the population of Japanese beetles considerably, versus growing turf between the rows. Accordingly, if you minimize the amount of turf in your yard, the population of Japanese beetles will decrease also.
Hand Pick and Destroy
By far the most effective natural way to get rid of Japanese beetles is to hand pick and destroy them. They will perish if dropped into a container of soapy water. If you're squeamish about touching them, set a container of water beneath the affected plant and give the plant a good shake. The beetles will fall off the plant into the container of soapy water and perish.