Adult Corn Rootworms Trap Update (08/05/21)
Adult corn rootworms continue to emerge at low numbers, based on yellow sticky trapping. Based on total counts, 71% of collected rootworms were northern corn rootworm (NCR) adults and 29% were western corn rootworm (WCR) adults. NCRs were observed last week in corn fields near Casselton, Cass County, Shenford and Sheldon in Ransom County, and Colfax and Antelope in Richland County. WCRs were observed near Sheldon in Ransom County and Colfax in Richland County. Other counties scouted last week that had no corn rootworms were Barnes, Griggs, Steele, Trail, and Grand Forks.
All fields were below the economic threshold (E.T.) of >2 beetles per trap per day (or >56 beetles per 4 traps per week as shown in Table 1). If above E.T., a high corn rootworm population is expected the following year and a corn rootworm management tool will likely be necessary to protect the following year’s corn crop.