State agriculture departments are stepping up eradication efforts against the destructive Japanese beetle, an East Coast pest that appears to be gaining a foothold in much of the West.
Washington State Department of Agriculture officials on June 29 caught 415 Japanese beetles on the first day of checking the traps they recently installed in the Yakima River Valley, where discoveries last year were the first to occur far inland from the ports and entryways where they're normally found.
The traps were placed in Yakima County near areas where WSDA trapped just three beetles last year and where a Grandview resident reported finding dozens of the beetles on her roses last summer.
"Given the damage these beetles can do, finding so many beetles so quickly is definitely concerning,” said Greg Haubrich, the WSDA's pest program manager. “It further illustrates how important this year will be for determining how large of an infestation we have in Washington. While our traps will provide critical data, residents reporting Japanese beetle sightings continues to be incredibly important.”
Unencumbered by the natural predators of its native Japan, the beetle -- Popillia japonica -- are a noted pest of about 300 species of plants, including grapes, hops, apples, walnuts, plums, peaches, roses, berries and spinach, according to the Canadian Food Inspection Agency.
Introduced back East
The shiny, coppery insect was first found in the United States in a nursery in New Jersey in 1916, where it is believed to have been imported with iris bulbs from Japan, the California Department of Food and Agriculture explains.
Since then, populations have spread throughout the East Coast and Midwest, causing an estimated $450 million a year in damage to home gardens and agricultural crops.
Active during the summer months, Japanese beetles can spread by someone moving from an affected area with a potted plant, the CDFA advises. Their eggs and larvae live in soil and can be easily transported by accident, hidden from view deep in the soil.
The adult beetles damage plants by skeletonizing the foliage, consuming only the leaf material between the veins as well as fruit on the plants, while the subterranean larvae feed on the roots of grasses, scientists say.
The beetles are considered an East Coast problem, but only nine Western states were free of them as of 2015, according to the USDA's Animal and Plant Health Inspection Service.
Several Western states are aggressively treating for the pest, including Oregon, where a state economic analysis concluded that farmers would face estimated costs of $43 million annually to manage it if it became established.
Spreading in the West
Despite the efforts, the Japanese beetle appears to be spreading. For instance, it had not been found in Wyoming until last August, when about 250 beetles were captured in a city park in Sheridan, on the state's northern tip, reported Sheridan Media.
Utah has had exclusion efforts since 1991 and reported a reduction in finds around Salt Lake City last year, but the state Department of Agriculture and Food found increases and new populations in several neighboring counties, according to the agency.
In response, the UDAF declared an Insect Emergency Infestation this spring and plans to contract a licensed commercial pest control operator to apply a non-restricted use pesticide in affected areas, the agency reported.
In Montana, Department of Agriculture Nursery Program is planning to distribute pesticide to homeowners in a Billings neighborhood to control the Japanese beetle population. Applications were expected to continue through October in a 4.1-square-mile section of the city, according to the MDA.
Because the beetle is a serious threat to many of California’s thriving industries, including nurseries, turf grass, and specialty crops, the CDFA sprays for it on an annual basis and so far has prevented establishment of the pest in the Golden State, notes the University of California's Statewide Integrated Pest Management Program.
In 2019, CDFA caught Japanese beetles near airports in Burbank, Los Angeles, Ontario, Sacramento, San Diego, Santa Ana, and Stockton, according to the UC.
Where the Japanese beetle is established in the Eastern U.S., it is managed with broad-spectrum insecticides and more selective microbial insecticides such as Bacillus thuringiensis galleriae and Heterorhabditis species entomopathogenic nematodes, UC IPM explains.
Traps are available for selectively attracting and capturing the adults. But traps can actually increase the number of beetles feeding on leaves and grass roots because only a portion of the attracted beetles are captured. the program warns.
So officials in Washington state and elsewhere have asked residents to be on the lookout.
“Last year’s Asian giant hornet project proved that the public can play a game-changing role in detecting and eradicating invasive species,” said Sven Spichiger, WSDA managing entomologist. “Japanese beetle poses every bit as much of a threat to farms and gardens as the Asian giant hornet. This is another case where the public can have a profound impact on the success of this detection and eradication project by reporting what they see in their communities.”