Japanese Beetle Season Begins

There have been two reports of Japanese beetle sightings for 2014: late last week from Lyon County and early this week from Franklin County. The beetles will continue to emerge over the next 2 weeks or so, especially following a soil softening rain. Individual beetles live for about 5 weeks; the season usually lasts for 6 to 8 weeks, peaking in mid-July.


Many insecticides are labeled for use against adult Japanese beetles, if control is needed. Pyrethroid products such as cyfluthrin, bifenthrin, deltamethrin, l-cyhalothrin, and permethrin can provide about 2 weeks of residual protection. Carbaryl can give 5 to 7 days of control. These products are toxic to bees and repeated applications can contribute to spider mite infestations.

Botanical alternatives, such as neem or pyrethrins, can give short-term protection from light to moderate beetle pressure. Insecticidal soap; extracts of garlic, hot pepper, or orange peels; and companion planting, however, are generally ineffective.

Continued physical removal of beetles or use of protective netting will help to minimize damage when beetles are not numerous. Individual beetles do not eat much, but if undisturbed, more will arrive and damage will intensify.

Treat foliage thoroughly and repeat as needed to prevent re-infestation during the adult flight period. Follow label directions and avoid spraying under windy conditions or when bees are foraging. Be sure the insecticide is registered for use on the plant or crop you intend to spray. If it is a food crop, note the minimum number of days that must be observed between the date of the last application and the date of harvest.

Japanese beetle traps will attract more beetles than they capture and are likely to result in more damage than if they were not present.

Grub control treatments will reduce damage to turf, but they will not reduce adult numbers during the following season because of the flight ability of the beetles.


By Lee Townsend, Extension Entomologist

Posted in Landscape Trees & Shrubs