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ViewAttendees 4

10-Minute Paper

Physiology, Biochemistry, and Toxicology

PBT: Toxicology

Incipient resistance of the African maize stemborer, Busseola fusca (Lepidoptera: Noctuidae) to MON89034 maize in South Africa

Sunday, November 5, 2023
3:06 PM – 3:18 PM ET
Location: Gaylord National Resort & Convention Center, Maryland 3-4
In-Person

Cry1Ab maize that control lepidopteran stemborers have been grown in South Africa since 1998. The resistance of Busseola fusca, which was documented in 2006, was mitigated by introducing MON 89034 maize, which expresses Cry1A.105 and Cry2Ab2 proteins. The first reports of B. fusca infestations of MON 89034 maize came in the KwaZulu-Natal province (2017/18 season), followed by reports in the Mpumalanga province (2022/23 season). In this study we report on artificial diet and plant-based laboratory assays done to assess the susceptibility of B. fusca populations sampled from three localities to the Bt proteins in MON 89034 and compare the results to those of five other populations. Protein bioassays indicated that only the Cry2Ab2 protein is efficacious against B. fusca, though Cry2Ab2 is much more effective than the Cry1Ab protein present in MON 810.  Survival on leaf tissue of MON 89034 plants ranged between 75 and 91% for the three problematic populations, compared to 0.4 to 9.6% of the other field-collected populations. At 21 days, survival on MON 89034 leaf tissue ranged between 41% and 74%.  Survival of the eight populations on Cry1Ab maize ranged from 13 to 43.6% and did not differ from that on non-Bt maize for most populations. The three populations therefore have resistance to Cry2Ab2 protein and therefore to MON 89034 maize. The results show that MON 89034 in South Africa is effectively a single-mode-of-action technology against B. fusca. This research emphasizes the importance of resistance monitoring and implementation of effective insect resistance management tactics.