Poster # 105

Joseph Chonza ¹, Isaack Kikway ¹, Jorge Valle ¹, and Pierce A. Paul ¹
1. The Ohio State University, CFAES Wooster Campus, Wooster, OH 44691
Corresponding Author: PH: 330.263.3842; Email: paul.661@osu.edu

Chonza, Joseph

chonza.1@buckeyemail.osu.edu

Fusarium head blight (FHB), caused by the fungus Fusarium graminearum, may significantly reduce wheat yield and lead to grain contamination with mycotoxins such as deoxynivalenol (DON). FHB epidemics are favored by warm temperatures, frequent rainfall, and high relative humidity. Consequently, fungicides are most warranted for FHB/DON management under wet, rainy conditions, but these same conditions may compromise fungicide efficacy. A field experiment was conducted during the 2024–2025 growing season to investigate the rainfastness of Miravis Ace, Prosaro Pro, and Sphaerex when applied at anthesis, with or without the non-ionic surfactant Induce, and subjected to simulated rainfall treatments. The experimental design was a randomized complete block, with a split-split arrangement of surfactant as the whole plot, rainfall treatment as the sub-plot, and fungicide treatment as the sub-sub-plot. Each fungicide treatment was applied to a separate sub-sub-plots within each sub-plot, after which each sub-plot within each whole-plot was either subjected to rainfall beginning 0, 15, 30, 45, 60 min post-application or received no rainfall. FHB index (IND) was estimated at Feekes growth stage 11.2, and harvested grain samples were assayed for DON. Tested fungicides reduced mean IND and DON when compared to the non-treated check. However, the magnitude of the treatment effect depended on the fungicide, whether or not a surfactant was used, and rainfall timing. Efficacy decreased when rain occurred right after or within 15 min of fungicide application. This loss in efficacy was more noticeable when the surfactant was not used. Miravis Ace and Sphaerex performed more consistently across all rainfall timings, while the efficacy of Prosaro Pro was affected by early rainfall start times, particularly without surfactant. When rainfall occurred 45 to 60 min after fungicide application, differences in mean IND and DON between rainfall and no-rainfall treatments were relatively small. In the absence of simulated rain, all fungicides performed well at reducing DON, with Miravis Ace plus Induce showing the greatest efficacy. As the interval between fungicide application and rainfall increased to 30–60 minutes, DON concentrations decreased to levels comparable to those observed in the absence of rainfall. This suggests that the tested fungicides were generally rainfast within about an hour after application. The use of Induce consistently lowered DON levels across treatments, showing that it likely enhanced fungicide adherence and effectiveness, and consequently, rainfastness.

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