The Portage County University of Wisconsin-Extension (UW-Extension) office recently reported it has received an increase in calls regarding the Japanese beetle, some callers stating there are thousands of them eating every plant in sight.

This non-native beetle was first found in New Jersey in 1916 and has since spread to the Midwest. The adult Japanese beetle feeds on a wide variety of fruits, vegetables, trees, shrubs and flowers eating the soft tissue between the veins leaving a lace-like skeleton. Portage County’s milder winter has played a factor in the increased beetle population this year. 

According to UW-Madison entomologist Patrick Liesch, residents are going to keep seeing these insects through the end of August.

Options for residents to combat the beetle:

Hand picking – The presence of beetles on a plant attracts more beetles. Daily removal will reduce the number by half compared to plants that allow the beetles to accumulate.

Beetles can be killed by knocking them into a bucket of soapy water.

Chemical control – Many landscape sprays will control adult beetles but may need to be applied every five to 10 days. Read the product label.

Don’t use traps – Although they capture thousands of beetles, research shows that plants near traps get much more damage than plants in areas with no traps. Beetles are drawn into trap areas, and those that are not captured are more likely to lay eggs in turf areas nearby. 

During the summer months, the Portage County UW-Extension office has a part-time master gardener/horticulture assistant to help with all things horticulture: plant and insect identification, plant diseases, gardening tips, soil and turf testing and more. He is available Tuesday through Friday from 9 a.m. until 1 p.m. and can be reached at 715-346-1589 or via email at [email protected]

For information regarding this or other questions, contact the Portage County UW-Extension office, 715-346-1316 or [email protected]