Our help is needed to stem Japanese beetle attack
It's been called the most devastating of all insects for yards, gardens and lawns, and we have reason for concern. An alert has been issued by the North Dakota Department of Agriculture because on June 21 larvae of the Japanese beetle were discov...
It's been called the most devastating of all insects for yards, gardens and lawns, and we have reason for concern. An alert has been issued by the North Dakota Department of Agriculture because on June 21 larvae of the Japanese beetle were discovered in nursery stock distributed throughout North Dakota by Minnesota's Bailey Nursery, who is the region's largest supplier of trees and shrubs.
Japanese beetle is extremely devastating because it devours over 300 species of plants, including trees, shrubs, perennials, annuals, fruits, vegetables and turf grass. Farmers have reason for concern because Japanese beetles consume soybeans and corn.
The beetle first entered the United States in 1916 in New Jersey from Japanese imports, and it's been marching westward ever since. It's now found in every state east of the Mississippi plus areas of Minnesota, South Dakota, Montana and Nebraska. Japanese beetles have been caught in monitoring traps in North Dakota each year since 2012, but the population remains low because the insect struggles to survive our winters. Even so, their presence is alarming because insects have natural abilities to adapt and evolve themselves quickly with each new yearly generation.
I first wrote about Japanese beetles back in August 2013, when we were cautioned the insect was found in monitoring traps. Charles Elhard, plant protection specialist with the North Dakota Department of Agriculture, indicated in a 2016 report that 386 beetles had been caught in traps last year. Once again property owners are being asked to check yards, especially trees and shrubs purchased this year, because of the new influx of infected nursery stock.
The adult Japanese beetle is rounded-fat, one-half inch long and metallic green in color with copper-bronze wing covers. The grub-like larva stage, which lives in the soil, are C-shaped, one-inch long with brown head, and have a pattern of hairs on the last body segment that forms a V-shape.
Adults emerge from the soil in summer, feed voraciously on vegetation and lay up to 60 eggs back in the soil before their 2-month lifespan ends. The eggs hatch in about two weeks into larvae that feed hungrily on the roots of plants, especially lawngrass and field crops. The larvae tunnel deeper into the soil to survive winter, and emerge as adults the next summer, and the cycle continues. Japanese beetles can also fly great distances.
Adult beetles feed heavily on nearly all plant material, with linden, birch, maple, apple, raspberry, rose and lawngrass being among their many favorites. Leaves are skeletonized, leaving only the veins. The larva stage feeds on the roots of lawngrass, causing ever-widening dead patches that can be lifted up as roots are destroyed.
Luckily, there are many insecticides that control Japanese beetle, which is listed on the label of many products. The active ingredients bifenthrin, imidacloprid or permethrin are most effective, according to university sources. If found in small numbers, beetles can be hand-picked and dropped in a bucket of soapy water. Control can be aimed at both adult beetles and soil larvae.
Japanese beetle traps contain attractants specific to the species, but are best used only for monitoring their presence, rather than for control. Research by University of Kentucky found that the traps actually attract Japanese beetles into an area in addition to those caught. But traps are important for detecting the beetles' presence in new areas. Currently the North Dakota Department of Agriculture has over 1500 traps monitoring the state.
How to help
The NDDA asks us to be on the lookout for Japanese beetles, and report any we find by contacting their Plant Industries Bismarck Division at (701) 328-2232.
With surveillance, maybe we can prevent this damaging insect from becoming widely established.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler's Greenhouse in Fargo. Readers can reach him at email@example.com .
He also blogs at growingtogether.areavoices.com.