Transgenic Bt corn, soil insecticide, and insecticidal seed treatment effects on corn rootworm (Coleoptera: Chrysomelidae) beetle emergence, larval feeding injury, and corn yield in North Dakota

Authors: CALLES-TORREZ, VERONICA - North Dakota State University; KNODEL, JANET - North Dakota State University; BOETEL, MARK - North Dakota State University; DOETKOTT, CURT - North Dakota State University; PODLISKA, KELLIE - North Dakota State University; RANSOM, JOEL - North Dakota State University; BEAUZAY, PATRICK - North Dakota State University; French, Bryan; FULLER, BILLY - South Dakota State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2017
Publication Date: 2/9/2018
Citation: Calles-Torrez, V., Knodel, J.J., Boetel, M.A., Doetkott, C.D., Podliska, K.K., Ransom, J.K., Beauzay, P., French, B.W., Fuller, B.W. 2018. Transgenic Bt corn, soil insecticide, and insecticidal seed treatment effects on corn rootworm (Coleoptera: Chrysomelidae) beetle emergence, larval feeding injury, and corn yield in North Dakota. Journal of Economic Entomology. 111(1):348-360. https://doi.org/10.1093/jee/tox297.
DOI: https://doi.org/10.1093/jee/tox297

Interpretive Summary: Northern, Diabrotica barberi Smith & Lawrence, and western, D. virgifera virgifera LeConte, corn rootworms are economic pests of corn, Zea mays L. in North America. Corn hybrids expressing Bacillus thuringiensis (i.e., Bt) proteins are widely used corn rootworm management tools. However, some D. v. virgifera populations in the north central U.S. have developed resistance to the Cry3Bb1 Bt protein. We sought to determine the impacts of Bt corn, tefluthrin soil insecticide, and clothianidin insecticidal seed treatment on rootworm larval feeding injury and adult emergence in eastern North Dakota (ND). Hybrids expressing Cry3Bb1, Cry34/35Ab1, and pyramided (Cry3Bb1 + Cry34/35Ab1) Bt proteins were tested. Beetle emergence and larval feeding injury were assessed at five locations from 2013 to 2015. Larval feeding injury was consistently lower in Bt-protected plots than in non-Bt corn. The lowest overall feeding injury and beetle emergence levels occurred in plots planted with the Cry3Bb1 + Cry34/35Ab1 pyramided hybrid. In most cases, beetle emergence was significantly lower in Bt-protected corn than in non-Bt hybrids. Exceptions included Wyndmere, ND (2013), where D. barberi emergence in Cry34/35Ab1 plots was not different from that in non-Bt corn, and Arthur, ND (2013), where D. v. virgifera emergence in Cry3Bb1 plots did not differ from that in the non-Bt hybrid. Cumulative emergence of both species at 50% was 6 to 7 d later from Bt-protected than from non-Bt hybrids. Tefluthrin and clothianidin were mostly inconsequential in relation to beetle emergence and larval feeding injury. These findings suggest that, although Bt corn currently provides effective protection from rootworm feeding injury in ND, some D. barberi and D. v. virgifera populations are likely developing resistance to Cry34/35Ab1 and Cry3Bb1, respectively.

Technical Abstract: Northern, Diabrotica barberi Smith & Lawrence, and western, D. virgifera virgifera LeConte, corn rootworms are economic pests of corn, Zea mays L. in North America. Corn hybrids expressing Bacillus thuringiensis (i.e., Bt) proteins are widely used corn rootworm management tools. However, some D. v. virgifera populations in the north central U.S. have developed resistance to the Cry3Bb1 Bt protein. We sought to determine the impacts of Bt corn, tefluthrin soil insecticide, and clothianidin insecticidal seed treatment on rootworm larval feeding injury and adult emergence in eastern North Dakota (ND). Hybrids expressing Cry3Bb1, Cry34/35Ab1, and pyramided (Cry3Bb1 + Cry34/35Ab1) Bt proteins were tested. Beetle emergence and larval feeding injury were assessed at five locations from 2013 to 2015. Larval feeding injury was consistently lower in Bt-protected plots than in non-Bt corn. The lowest overall feeding injury and beetle emergence levels occurred in plots planted with the Cry3Bb1 + Cry34/35Ab1 pyramided hybrid. In most cases, beetle emergence was significantly lower in Bt-protected corn than in non-Bt hybrids. Exceptions included Wyndmere, ND (2013), where D. barberi emergence in Cry34/35Ab1 plots was not different from that in non-Bt corn, and Arthur, ND (2013), where D. v. virgifera emergence in Cry3Bb1 plots did not differ from that in the non-Bt hybrid. Cumulative emergence of both species at 50% was 6 to 7 d later from Bt-protected than from non-Bt hybrids. Tefluthrin and clothianidin were mostly inconsequential in relation to beetle emergence and larval feeding injury. These findings suggest that, although Bt corn currently provides effective protection from rootworm feeding injury in ND, some D. barberi and D. v. virgifera populations are likely developing resistance to Cry34/35Ab1 and Cry3Bb1, respectively.