Pheromone trapping for European corn borer ecotypes in North Dakota corn

European Corn Borer (ECB), Ostrinia nubilalis, (Lepidoptera: Crambidae) is an economic pest in corn, Zea mays L., as well as other crops in the U.S. Populations of ECB have declined since the introduction and widespread adoption of corn hybrids expressing Bacillus thuringiensis (Bt) toxins. Our goal was to monitor ECB flights of the univoltine (Z-race) and bivoltine (E-race) ecotypes in the major corn producing areas of North Dakota. Two modified Hartstack wire traps were placed in grassy ditches along corn field edges. One trap was baited with a Z-race lure and the other trap with an E-race lure. Traps were monitored weekly for moths from early June to mid-August at 10 and 12 field sites in 2020 and 2021, respectively. A total of 1,172 Z-race ECB and 14 E-race ECB moths were trapped from all field sites in 2020. Peak activity for the Z-race occurred the second week of July 2020. Finley (Steele Co.) had the highest number of the Z-race, a total of 252 moths, followed by Buffalo (Cass Co.) with 225 moths in 2020. Casselton (Cass Co.) had the highest number of the E-race, only a total of eight moths in 2020. Additional data from the 2021 field season will be discussed. Based on previous low trapping records, ECB populations are currently increasing in North Dakota corn.