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

Abstract

Mycotoxins 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.

Insect ear‐feeding impacts Gibberella ear rot and deoxynivalenol accumulation in corn grain

“…In contrast, the effective Vip3A hybrids used in 2018 reduced IFI by >70% across all locations (Table 2). Similar reductions were recently observed by Kaur et al (2023) in silage corn. However, a significant reduction in ear rot and DON in the Vip3A hybrid occurred only at Huron, which had both ideal conditions for fungal infection after silking and significant WBC injury in noneffective hybrid.…”

“…Smith et al (2018) found that a prothioconazole application at silking in corn did not result in lower ERS compared to a non-treated control. In a recent study in Michigan silage corn, prothioconazole reduced ERI at only two, and DON at four, of 11 site-years (Kaur et al, 2023). Our study reiterates that fungicide applications for ear mold protection in the Great Lakes region are complicated and often have minimal positive return for the grower.…”

Establishment of Alfalfa Intercropped under Corn in Response to Varying Rates of Prohexadione with or without Fungicide Plus Insecticide

“…Corn populations and yields in both years were moderate and suitable for good to excellent establishment of interseeded alfalfa treated with PHD followed by FI [3]. Previous work [10,13,[22][23][24] found that directed spray applications of prohexadione on alfalfa and broadcast applications of fungicide and insecticide had little or no impact on corn silage yield. Prior to and 6 weeks following the application of FI, populations of PLH near the research sites were below the economic thresholds set for insecticide treatment of alfalfa over 20 cm in height [25].…”

Planting time and seeding rate impact insect feeding, ear rots, and forage nutritive value in silage corn

“…Both percent ERS and IFS were estimated by counting the total number of damaged kernels on each of the affected ears in a plot divided by the total number of kernels on 10 examined ears in it. All ratings were quantified on a per plot basis (Kaur et al, 2023).…”

“…The most commonly occurring ear rots in the Great Lakes region are the pink ear rot, caused by Fusarium graminearum (Schwabe [anamorph or asexual stage of Gibberrella zeae Schweinitz Petch]), and the white or Fusarium ear rot, caused by Fusarium verticilloides (Saccardo) Nirenberg (Munkvold, 2003;Sutton, 1982). The injury due to ear-damaging insects can considerably increase the ear rot severity (ERS) due to husk wounds and facilitate infection pathways for fungi (Farhan et al, 2020;Kaur et al, 2023;Singh et al, 2023). Infections by these fungi can also result in the production of mycotoxins (secondary toxic metabolites), which can make silage corn unfit for livestock consumption (Munkvold et al, 2019;Ogunade et al, 2018).…”