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Student 10-Minute Presentation Competition

Plant-Insect Ecosystems

Student Competition

Student

Grad 10-min Competition: P-IE, Insecticides

Resurgence of an old threat: Evolution of Diatraea grandiosella (Lepidoptera: Crambidae) resistance to Bacillus thuringiensis (Bacillales: Bacillaceae) proteins in New Mexico

Monday, November 10, 2025
9:48 AM - 10:00 AM Pacific
Location: Oregon Convention Center, E147-148, OCC
Oral Presentation Student Competition
Diatraea grandiosella (Dyar) (Lepidoptera: Crambidae), commonly known as the southwestern corn borer (SWCB), is a significant pest of maize, primarily causing yield losses through stalk tunneling and plant lodging. The introduction of genetically modified corn expressing Bacillus thuringiensis (Berliner) (Bacillales: Bacillaceae) (Bt) insecticidal proteins has significantly reduced D. grandiosella as an economic pest in the United States. However, in 2023, severe damage attributed to D. grandiosella was reported in Antelope Wells, New Mexico, on corn hybrids expressing the Bt proteins Cry1Ab and Cry1F. In 2024, similar injuries were observed on hybrids expressing Cry1A.105, Cry1F and Cry2Ab2. In this study, we investigated Bt resistance in SWCB larval in southwest New Mexico. We conducted dose-response diet-overlay bioassays using a laboratory-susceptible SWCB strain to estimate the diagnostic concentration for Cry1A.105, Cry1F, Cry2Ab2, and Vip3Aa39 proteins. Subsequently, F2 screens were performed using two field populations collected in 2023 and 2024 from Antelope Wells, New Mexico to estimate resistance allele frequencies for these proteins, followed by full-range dose–response bioassays on F2 survivors. Estimated resistance allele frequencies were 0.1275 for Cry1A.105, 0.1381 for Cry1F, 0.0814 for Cry2Ab2, and 0.0000 for Vip3Aa39. Resistance ratios were approximately 200-fold for Cry1A.105, 55-fold for Cry1F, and over 11-fold for Cry2Ab2. No resistance was detected to Vip3Aa39. These findings provide evidence for the evolution of Bt resistance in D. grandiosella to Cry proteins, likely contributing to the observed injuries through reduced susceptibility in these populations. Continued research on resistance management is essential for sustainable pest management of SWCB.