Pheromone trapping for European corn borer in field corn of North Dakota

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 adoptions of corn hybrids expressing Bacillus thuringiensis (Bt) toxins. Our objective was to monitor ECB flights of the univoltine (Z-race) and bivoltine (E-race) ecotypes in east central and southeastern of North Dakota. Two Hartstack wire traps were placed on a grassy field edges. One trap was baited with a Z-race lure and the other trap with an E-race lure. Moths were monitored weekly from mid-June to mid-August at 10 field sites in seven counties. A total of 1,172 Z-race ECB and 14 E-race ECB moths were counted during the trapping period from all field sites. Peak activity for the Z-race was during the second week of July in most. Finley in Steele Co. had the highest number of the Z-race, a total of 252 moths, followed by Buffalo (Cass Co.) with 225 moths. The lowest numbers of Z-race moths were observed at Cuba (Barnes Co.) and Mooreton (Richland Co.). Casselton in Cass Co. had the highest number of the E-race, only a total of eight moths. No E-race ECB was observed at five field sites. Based on previous low trapping records for ECB, our 2020 trapping data indicates that ECB populations are increasing in North Dakota. One reason for this increase could be the rise of conventional non-Bt corn plantings due to corn markets.