Impact of Gibberella Ear Rot on Grain Quality and Yield Components in Maize as Influenced by Hybrid Reaction.

The impact of Gibberella ear rot (GER; caused by Fusarium graminearum) on deoxynivalenol (DON) contamination of grain and yield components in maize were investigated using data from 30 environments in Ohio (3 years by 10 locations). Fifteen hybrids, later classified as susceptible (SU), moderately susceptible (MS), or moderately resistant (MR), based on the magnitude of differences in mean arcsine square-root-transformed GER severity (arcSEV) and log-transformed DON (logDON) relative to a reference SU check, were planted in each environment, and 10 ears per hybrid were inoculated with a spore suspension of F. graminearum. Relationships between GER severity and DON were well described by a Kono-Sugino-type nonlinear equation. Estimated parameters representing height (A) and steepness (ß) of the curves were significantly higher for SU than MS and MR hybrids but A was not significantly different between MS and MR. Results from a surrogacy analysis showed that GER was a moderate trial- and individual-level surrogate for DON. Both grain weight per ear and ear diameter decreased with increasing arcSEV but the regression slopes varied among resistance classes. The rates of reduction in both yield components per unit increase in arcSEV were significantly greater for SU than for MS and MR. An estimated 50% reduction in grain weight occurred at 62% GER severity for SU, compared with 77% severity for MS and 83% for MR. These results show that GER severity can be used as a surrogate for early estimation of DON contamination and yield loss to help guide grain handling and marketing decisions.

Evaluating the Profitability of Foliar Fungicide Programs in Mid-Atlantic Soft-Red Winter Wheat Production.

In mid-Atlantic soft-red winter wheat (SRWW) production, the standard timing for a fungicide application is between flag leaf emergence (Feekes growth stage [FGS] 8) and heading (FGS 10.5). However, two-pass and anthesis (FGS 10.5.1) applications are becoming common, although these programs have not been thoroughly evaluated for disease control, yield, and profitability. Experiments were conducted in the mid-Atlantic in 2015 and 2016 to evaluate fungicide programs with applications at FGS 8, FGS 10.5.1, and two-pass programs with an early application at green-up (FGS 5) followed by (FB) applications at either FGS 8 or FGS 10.5.1. Fungicide programs that included an application at FGS 10.5.1 resulted in the highest probability of no disease on the flag leaf (0.29 to 0.40). The estimated mean yield increases ( D¯ ) relative to the nontreated check ranged from 253.65 to 634.16 kg ha-1. Using a grain price of $0.18 kg-1 ($5 bushel-1), probabilities were similar between applications at FGS 8 (0.49 to 0.56) and FGS 10.5.1 (0.53). The probability of profitability ranged from 0.48 to 0.57 for FGS 5 FB FGS 8 applications and 0.52 to 0.59 for FGS 5 FB FGS 10.5.1 applications, indicating limited benefit to two-pass programs.