Strategies for Managing Mycotoxins, Ear Rots, and Ear Damaging Insects in Corn SilageDOWNLOAD FILE
Mycotoxin accumulation in corn (Zea mays L.) silage due to ear rot infections by certain ascomycete fungi cause grave health issues in livestock. Infections have intensified lately, with increased ear-damaging insect flight and favorable environment in the Great Lakes region. A survey across Michigan counties confirmed presence of at least 10 mycotoxins. Therefore, evaluating strategies such as hybrid selection and fungicide against insects, ear rots, mycotoxin accumulation, and silage quality is crucial. Field trials were conducted in a randomized complete block design at ten site years across 2019-21. Hybrids from three classes (two each) were used: non-Bt (BtN); 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). Proline 480SC @ 416.5 ml/ha was applied at silking in a subset of plots. Insect and disease pressure was low across site years, except Huron 2020 and Ingham 2019 and 2020. Eighty to ninety percent less insect damage was observed in BtEW than BtN hybrids. Hybrids BtEW also showed lower ear rot indices than BtN hybrids. A strong correlation (R2 = 0.53) between insect damage and ear rot severity was seen at Huron 2020, site with high insect pressure. Mycotoxin concentration, particularly deoxynivalenol (DON), was also low in BtEW. Weak correlations were observed between ear damage and mycotoxin concentration. Fungicide application did not reduce ear rot infections when disease incidence was >20%. However, under low disease pressure, ear rot incidence and DON reduced by 50-70 percent in treated plots. Quality was mostly similar across treatments. Overall, results indicated that, use of hybrid insect protection trait can help to reduce insect feeding, disease occurrence, and mycotoxin accumulation, especially under high insect pressure conditions where fungicides might fail to provide a consistent control.