Influence of Bt and environmental factors on Fusarium ear rot in maize

Fusarium verticillioides is responsible for Fusarium ear rot (FER) and fumonisin (FUM) in maize (Zea mays L.). Multiple factors, including drought stress, humidity, and insects, influence the severity of FER and FUM. This study aimed to assess the occurrence and severity of FER, FUM, and corn earworm (Helicoverpa zea Boddie) feeding in Bt (Bacillus thuringiensis) and non-Bt maize grown on commercial farms in North Carolina. We attempt to identify important environmental factors specific to maize growth stages that contribute to FER and FUM. Two Bt and three non-Bt hybrids were sampled in 50 environments in North Carolina for FER and FUM under natural infection. Bt hybrids had 7.2% ear rot compared to 11.7% for non-Bt hybrids. For corn earworm feeding, Bt hybrids had 1.5 cm² per ear of feeding damage compared to 4.2 cm² per ear for non-Bt hybrids. Although differences in FUM were not significant, Bt hybrids had a numerically lower FUM than non-Bt hybrids. In some counties and years, the FUM levels exceeded those recommended for products intended for human and animal consumption, with the highest level recorded at 27.8 ppm in a non-Bt hybrid. We identified several environmental covariates related to FER, FUM, and corn earworm feeding. The results highlight the complexity of ear rots, mycotoxin, and insects and their interaction in maize. It also highlights a need for a larger sample size in multiple environments with adequate variation in FER, FUM, and insect feeding to tease apart factors influencing ear rots and mycotoxins.