(2nd Place) On-farm comparison of Bt and non-Bt refuge corn hybrids for yield and feeding by Helicoverpa zea

Helicoverpa zea (Bodie) is a prominent pest in the southeastern United States that has evolved resistance to Cry toxins in corn and cotton. To delay resistance evolution, growers in this region are required by law to plant at least 20% of their corn area with refuge non-Bt corn seed. However, most growers do not do this. Despite the fact multiple published small-plot studies show that timely-planted non-Bt and Bt hybrids yield equally, they often perceive non-Bt hybrids to yield less than Bt hybrids. In response, our work compared non-Bt and Bt hybrids planted in strips using grower equipment. In 2022, we planted four corn hybrids (Bt- P1197 YHR, DKC 65-99, non-Bt- P1197 LR and DKC 67-70) as strip plots in 27 different locations throughout North Carolina; in 2023, we planted the same hybrids in 28 fields. When corn reached dent (R5), we measured the area of H. zea injury (centimeters squared) from 40 ears in each hybrid at each location. Growers recorded yield at harvest. We hypothesized that yields between the Bt and non-Bt hybrids would not be significantly different, unless other environmental stressors (such as drought) were present. In the future, we plan to partner with economists to build an economic model to compare cost or profits from planting non-Bt or Bt hybrids. Results from this study will be crucial to persuade growers to plant non-Bt refuge corn to sustain the efficacy of Bt corn.