Yard & Garden Report


| Share

Japanese Beetle Alert

An estimated 5,000 beetle-infested plants were shipped to North Dakota this spring.

Japanese beetle
Japanese beetle skeletonizing leaf

Bad news:
  Japanese beetle larvae and pupae were discovered in nursery stock by the North Dakota Department of Agriculture on June 21, 2017.

Really bad news: The infested materials came from the same nursery in Minnesota where 80% of our state’s plants come from. An estimated 5,000 beetle-infested plants entered up to 67 nursery facilities in North Dakota since March. Our nurseries are examining their plants for Japanese beetles now, but 95% of plants have already been sold.

It’s possible that a new outbreak of Japanese beetles will soon emerge across our state.

Is this a big problem?

It could be. Japanese beetle is one of the most destructive of all insects in yards and gardens. It will attack more than 300 different species of plants. The beetles skeletonize leaves (see photo), and the grubs feed on turf roots. The pest is especially destructive of grape, apple, crabapple, chokecherry, rose, linden and turf.

Japanese beetle causes $450 million in damage each year in the U.S.A. It entered New Jersey in 1916 and has slowly headed our way over the past century. The pest has been in Minnesota for decades and became abundant in the Twin Cities in 2011. It is established now in South Dakota and has been detected in Montana. The pest has been detected every year in North Dakota since 2012 (see map), but its numbers remain low.

Japanese beetle survey map
Japanese beetle survey map for 2016.
What can we do?

Get to know this enemy and look for it—especially if you planted any trees or shrubs this spring. The beetles are emerging out of the soil now. Inspect the pots for cocoons.

Japanese beetle is easy to identify. The shiny pest is one-half-inch long, metallic green and has bronze wing covers (see photo). A series of six white tufts run along each side of its body.

If you find it, contact the North Dakota Department of Agriculture immediately (701.328.2232) or your local county Extension office.

Kill the pests. If there are only a few beetles, toss them into a bucket of soapy water. Keep monitoring daily, if possible, for new beetles to appear this summer. 

For major swarms, many insecticides (carbaryl, bifenthrin, pyrethrin, imidacloprid, permethrin and more) will kill the beetles. 

In the past, our greatest defense against Japanese beetle has been our bitter cold winters. Japanese beetles try to overwinter as grubs in the soil, but many freeze to death.

Today, our nurseries are working to prevent future outbreaks, but this is a daunting task. Gardeners need to join the battle. Our shared diligence and brutal winters can slow the spread of this pest. For more information, read Integrated Pest Management of Japanese Beetle in North Dakota and the NDSU Crop & Pest Report.

Written by Tom Kalb, Extension Horticulturist, North Dakota State University. Published in the NDSU Yard & Garden Report, July 3, 2017.

Elhard, C. and J. Knodel. 2017. Japanese beetle shipped into North Dakota. NDSU Crop and Pest Report. July 6, 2017. 
Knodel, J. and C. Elhard. 2017. Integrated Pest Management of Japanese Beetle in North Dakota.  

Photo courtesy of Steven Katovich, USDA Forest Service, Bugwood.org. Map courtesy of Jan Knodel and Charles Elhard, NDSU and NDDA, respectively. 

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.