Japanese beetles (Figure 1) have made a comeback so far this year with significant problems in some areas of the state. Reports from Ohio also indicate above-normal numbers.
Removing beetles by hand may provide adequate protection for small plantings, especially when beetle numbers are low. The presence of beetles on a plant attracts more beetles. Thus, by not allowing beetles to accumulate, plants will be less attractive to other beetles.
One of the easiest ways to remove Japanese beetles from small plants is to shake them off early in the morning when the insects are sluggish. Kill beetles by shaking them into a bucket of soapy water. Highly valued plants, such as roses, can be protected by covering them with cheesecloth or other fine netting during the peak of beetle activity.
Many insecticides are labeled for use against adult Japanese beetles. Examples include pyrethroid products such as cyfluthrin (Tempo, Bayer Advanced Lawn & Garden Multi-Insect Killer), bifenthrin (TalstarOne, Onyx), deltamethrin (Deltagard), lambda cyhalothrin (Scimitar, Spectracide Triazicide), esfenvalerate (Ortho Bug-B-Gon Garden & Landscape Insect Killer) and permethrin (Spectracide Bug Stop Multi-Purpose Insect Control Concentrate and other brands). Carbaryl (Sevin and other brand names) is also effective. The pyrethroid products generally provide 2 to 3 weeks protection of plant foliage while carbaryl affords 1 to 2 weeks protection.
For those seeking a botanical alternative, Neem products such as Azatrol or Neem-Away (Gardens Alive), or Pyola (pyrethrins in canola oil) provide about 3 to 4 days deterrence of Japanese beetle feeding. Insecticidal soap, extracts of garlic, hot pepper, or orange peels, and companion planting, however, are generally ineffective.
By Lee Townsend, Extension Entomologist