Hybrid insect protection and fungicide application for managing ear rots and mycotoxins in silage corn

Abstract

AbstractMycotoxins in silage corn (Zea mays L.) accumulate due to ear rot infections by certain ascomycete fungi and cause health issues in livestock. Fungal infections intensify with increase in ear‐damaging insect injury and favorable environment in the US Great Lakes region. Therefore, evaluating strategies such as hybrid insect protection and fungicide decisions to manage insects, ear rots, mycotoxin, and silage quality is crucial. Field trials were conducted in randomized complete block design at 11 Michigan site‐years across 2019–2021 using three hybrid insect protection levels under two levels of prothioconazole fungicide (treated and non‐treated). Hybrids (two per level) included: conventional (non‐Bt); Bt with Cry1F and Cry1Ab (BtE), protection only against European corn borer (ECB); and Bt with Cry1F and Vip3A (BtEW), protection against both ECB and western bean cutworm (WBC). Insect injury and ear rot index were 80%–90% and 75%–90% lower, respectively, in BtEW hybrids than non‐Bt hybrids. Strong correlation between insect injury and ear rot severity was observed when insect pressure was high. Mycotoxin levels, particularly deoxynivalenol (DON), was also lowest in BtEW hybrids. Weak correlations were observed between ear injury and mycotoxin concentration. Under low disease pressure, a 50%–70% reduction was observed in fungicide treated plots for both ear rot incidence and DON concentration. However, fungicide application did not reduce ear rot infections driven by high insect injury. Treatments had negligible impact on forage quality. Overall, results indicated that incorporating insect protection in hybrid selection decisions reduced insect feeding, disease occurrence, and mycotoxins, especially under high insect pressure.