URBANA, Ill. — Asian beetles and northern corn rootworm (NCR) continued to pace Illinois’ top 10 list of crop pests in 2022, according to an applied research report issued by the University of Illinois Cooperative Agriculture Pest Survey program. The study, issued Feb. 1 as part of the U of I Dept. of Crop Science’s 2022 Applied Research Report, estimates densities of common insect pests in corn and soybean cropping systems throughout the nine crop reporting districts in Illinois. 

Kelly Estes, State Survey Coordinator, Illinois Cooperative Agriculture Pest Survey Program, said 10 common insects were studied, with insects collected in sweep samples identified and counted to provide an estimate of the number of insects per 100 sweeps. 

“Pest populations once again remained relatively low during the 2022 growing season. Reports of pest issues were few throughout the growing season. Results from the survey did illustrate several areas of the state where pest pressure was higher,” Estes reported. 

“Japanese beetles continue to garner attention each summer, particularly following large numbers of Japanese beetles in 2017 and 2018. While we didn’t observe those kinds of populations in 2022, western and northwestern Illinois once again had higher numbers of Japanese beetles in sweep samples, particularly Adams (averaging 291 beetles/100 sweeps) and Lee county (120 beetles/100 sweeps). While the northeastern crop reporting district average was lower than the previously two mentioned, it is worth noting that DeKalb county recorded high Japanese beetle counts as well (average of 106 beetles/100 sweeps).” 

Because 2021 survey results yielded extremely high numbers of NCR in northeastern Illinois, surveyors paid extra attention to the count in 2022. Noticeable populations of northern corn rootworms were observed in several counties, according to the report. 

“These counties were spread through the northern and northwestern 13 part of the state with average per 100 sweeps much higher than district or state averages – DeKalb (69 beetles/100 sweeps), Warren (35 beetles/100 sweeps), Carroll (17 beetles/100 sweeps), and Lee (14 beetles/100 sweeps),” Estes found. 

The survey also discovered that populations of Dectes stem borer seem to be on the increase in the southern third of Illinois. “Washington, Perry, Saline and Hamilton all had significantly higher numbers of Dectes stem borer in sweeps compared to surrounding counties. Results varied from field to field and county to county, but it is evident that Dectes stem borer is well established in southern Illinois,” Estes said. 

It also revealed that much like 2021, western corn rootworm (WCR) beetle populations remained low in several areas of the state. However, higher numbers were observed in northwest Illinois, with Carroll and Lee counties reporting significantly higher numbers of WCR beetles in per plant counts. 

Population sweeps were also conducted for bean leaf beetle, grape colaspis, southern corn rootworm, grasshopper, cloverworm and stink bug. Results of the crop pest survey, along with the full U of I 2022 Applied Research Report, are now available for download online at https://go.illinois.edu/2022PestPathogenARB.