European Corn Borer Increasing (07/15/21)
European corn borer (ECB) Z-race moths (univoltine) were detected at 10 of the 13 of trap sites and ECB E-race (bivoltine) at 5 of the 13 trap sites last week (Table 1). ECB-Z is our dominant corn borer in ND and increasing trap counts were observed in Ransom County near Shenford and Nelson County near Lakota. First detections of ECB Z-race were observed at 6 trap sites: Cass County near Kindred, Griggs County near Cooperstown, Steele county near Finley, Traill County near Alton, Grand Forks County near Gilby/Mcanna, and Richland County near Antelope. We also detected the first E-race ECB moth at 4 trap sites: Cass County near Casselton, Traill County near Alton, and Ransom County near Shenford and Sheldon. Corn crop stages were V6 to V10.
The accumulated degree days (ADD; base 50⁰F) in ND for univoltine ECB-Z development range from 1095 in northern areas and 50% of moths emerged to >1400 ADD in southern areas and 100% of moths emerged (see map below). This indicates that the univoltine ECB moths are 50-100% emerged and 3rd instar larvae will be tunneling into the corn stalk. After the larvae are inside stalks, foliar insecticides are no longer effective for control of ECB. See last week’s Crop & Pest Report #11, July 8th for E.T for ECB.
Extension Crop Protection Specialist
NDSU North Central Research Extension Center