Front Range landscaper likely cause of Japanese beetle threat to western Colorado agriculture

The Colorado Department of Agriculture is funding additional efforts to eradicate a resurgence of ravenous Japanese beetles in Mesa County.

The pest was discovered in Grand Junction two years ago. A contractor from Colorado's Front Range - where 11 counties are "partially or totally infested" with the bugs, according to the state - is thought to have transported the beetles there in sod that was delivered to a residential landscaping project. 

The delivery was in violation of a quarantine the state put in place to prevent that very the spread of Japanese beetles from the those counties to other parts of Colorado. 

At risk are 300 species of plants, many of which are essential to western Colorado's agricultural economy, including peaches, sweet corn, and grapes. Many types of Western Slope grapes are harvested to produce wine. The beetles also attack many other ornamental plants in urban spaces, including turf grass. The beetles lay eggs in grass or turf. Their larvae hatch and consume grass roots.

The landscape contractor unloaded several large rolls of sod in the summer of 2022. The beetles were detected later that year, according to the CDA.  

The beetle was declared a public nuisance pest requiring eradication by Mesa County Commissioners on March 7, 2023.  

"We are profoundly grateful for the $110,000 grant from the CDA, which will significantly aid our efforts to eradicate the invasive Japanese beetle in Mesa County," stated Bobbie Daniel, Chair of the Mesa County Board of Commissioners, in a press release. "These funds will go a long way to strengthen our initiatives to eliminate as many Japanese beetles as possible, preventing further spread throughout the county. The grant will partially fund our 2024 spray program in the hot zone, where we are currently treating approximately 1,300 properties."  

Mesa County's Noxious Weed and Pest Management, the City of Grand Junction and the Colorado State University Tri-River Extension office have been coordinating since the insect's 2022 detection to set up traps that monitor the presence of the pest across the affected area. 

The additional state funding will lead to treatment of approximately 260 acres of turf within the Grand Junction area. The County will use Acelepryn SC, an insecticide shown to work to eradicate the Japanese beetle. According to a CDA spokesperson, the effectiveness of the treatment will be checked by testing the soil twice a year - in Spring and Fall - and measuring the amount of insecticide remaining to be active in the soil. Adult trapping will provide a clear picture of the insects' population and the effectiveness of the insecticidal treatment.  

 "CDA is committed to protecting the Western Slope from this voracious pest that feeds on both agricultural and decorative plants," stated Plant Industry Division Director Wondirad Gebru. "Based on our previous experience of eradicating the Japanese beetle, its complete eradication will take from five to six years but we should start seeing a dramatic decline in beetles in the second and third year of the treatment, hopefully this year and next."

The 11 Front Range counties (Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, El Paso, Jefferson, Larimer, Pueblo, and Weld) were quarantined in 2018. Almost a decade earlier, the state department of agriculture established an exterior quarantine in an attempt to prevent the insect from being transported from out of state.   

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It is the Western Slope's second war against the bug. Japanese beetles were first detected in Colorado in 1995, but a large outbreak occurred in 2002 in the area of Clifton and Palisade. Officials and business owners in the area around the Upper Grand Valley Pest Control District "acted decisively to eradicate the pest and reduced its population by 99% over five years" according to data, CDA spokesperson Olga Robak told CBS News Colorado.

"Scientists and experts were caught off guard by the ability of the pest to establish itself in our region, thinking that Japanese beetle, an insect that likes moisture and humidity would never become a problem in the semi-arid Colorado climate," as explained on CDA website dedicated to the insect. "However, our urban landscape areas are oases of green, irrigated plant material that the beetle loves to eat and thrive in.

"There is zero tolerance for this pest as it has high economic consequences."