European Corn Borer Decreasing (07/21/21)
European corn borer (ECB) Z-race moths (univoltine) were detected at 9 of the 13 of trap sites and ECB E-race (bivoltine) at 3 of the 13 trap sites last week (see Table 1 on next page). ECB-Z peaked last week and decreasing trap counts were observed this week (except for Sheldon in Ransom County and Colfax in Richland County). We also detected the first E-race ECB moth at one new trap site, Kindred, Cass county. Corn crop stages were V9 to VT.
Based on the accumulated degree days (ADD; base 50⁰F), the univoltine ECB-Z moths are 100% emerged in ND (see map next page). Most areas also have accumulated enough ADD for 3rd instar larvae to be tunneling into the corn stalk. After the larvae are inside stalks, foliar insecticides are no longer effective for control of ECB. See Crop & Pest Report #11, July 8th for E.T for ECB.
Extension Crop Protection Specialist
NDSU North Central Research Extension Center