Corn Rootworm Trap Update (08/12/21)
Adult corn rootworms continue to emerge at low numbers, based on yellow sticky traps. Based on total counts, 82% were northern corn rootworm (NCR) adults and 18% were western corn rootworm (WCR) adults. NCRs were observed last week in corn fields near Casselton - Cass County, Cuba – Barnes County, Shenford - Ransom County, and Colfax & Antelope - Richland County. WCRs were observed near Sheldon - Ransom County. No corn rootworms were observed in Griggs, Nelson, Steele, Traill, and Grand Forks counties.
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). When numbers are above the 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.