Modeling Yield Losses and Fungicide Profitability for Managing Fusarium Head Blight in Brazilian Spring Wheat

Abstract

Fusarium head blight (FHB) and wheat yield data were gathered from fungicide trials to explore their relationship. Thirty-seven studies over 9 years and 11 locations met the criteria for inclusion in the analysis: FHB index in the untreated check ≥ 5% and the range of index in a trial ≥ 4 percentage points. These studies were grouped into two baseline yields, low (Yl ≤ 3,631 kg ha−1) or high (Yh > 3,631 kg ha−1), defined based on the median of maximum yields across trials. Attainable (disease-free) yields and FHB index were predicted using a wheat crop and a disease model, respectively, in 280 simulated trials (10 planting dates in a 28-year period, 1980 to 2007) for the Passo Fundo location. The damage coefficient was then used to calculate FHB-induced yield loss (penalizing attainable yield) for each experiment. Losses were compared between periods defined as before and after FHB resurge during the early 1990s. Disease reduction from the use of one or two sprays of a triazole fungicide (tebuconazole) was also simulated, based on previous meta-analytic estimates, and the response in yield was used in a profitability analysis. Population-average intercepts but not the slopes differed significantly between Yl (2,883.6 kg ha−1) and Yh (4,419.5 kg ha−1) baseline yields and the damage coefficients were 1.60%−1 and 1.05%−1, respectively. The magnitudes and trends of simulated yield losses were in general agreement with literature reports. The risk of not offsetting the costs of one or two fungicide sprays was generally higher (>0.75) prior to FHB resurgence but fungicide profitability tended to increase in recent years, depending on the year. Our simulations allowed us to reproduce trends in historical losses, and may be further adjusted to test the effect and profitability of different control measures (host resistance, other fungicides, etc.) on quality parameters such as test weight and mycotoxin contamination, should the information become available.

Are DMI+QoI premixes applied during flowering worth for protecting wheat yields from Fusarium head blight? A meta-analysis

“…The presence of mycotoxins at certain levels may downgrade grain price or even reject the product at the elevators in countries where maximum limits have been promulgated ( ANVISA 2011;2017;McMullen et al 2012) . In Brazil, model-based estimates of relative losses to wheat yield due to FHB during more than 25 years averaged 10%, ranging from 3 to 25% (Duffeck et al 2020). The estimates of decadal averages in yield losses were in agreement with reports from field experiments that suggested FHB being of no economic importance prior to the 1990s (Casa et al 2004;Reis et al 1996).…”

“…A 28-year simulation study used the meta-analytic estimate of yield gain from a second spray of tebuconazole (Machado et al 2017) when linking historical weather, a crop model, a disease model, and a model relating FHB index and yield. Results of that study showed that the risk of not-offsetting the costs was generally higher for two sprays given the variability in the disease risk in the historical weather for a location in southern Brazil (Duffeck et al 2020).…”

Profitability of fungicide applications for managing soybean rust in scenarios of variable efficacy and costs: A stochastic simulation

“…Previous studies have addressed similar questions regarding the profitability of fungicides. In most cases, the analyses are based on meta‐analytic estimates of the mean and variance of the yield response, using large empirical data sets, for a range of combinations of fixed fungicide costs and crop prices (Barro et al, 2019; Duffeck et al, 2020; Molina et al, 2019; Machado et al, 2017; Paul et al, 2011; Shah & Dillard, 2006; Willbur et al, 2019; Wise et al, 2019).…”

Profitability of fungicide applications for managing soybean rust in scenarios of variable efficacy and costs: a stochastic simulation

“…Previous studies have addressed similar questions regarding the profitability of fungicides. In most cases, the analyses are based on meta-analytic estimates of the mean and variance of the yield response, using large size empirical datasets, for a range of combinations of fixed fungicide costs and crop prices (Barro et al , 2019;Willbur et al , 2019;Molina et al , 2019;Machado et al , 2017;Paul et al , 2011;Shah & Dillard, 2006;Wise et al , 2019;Duffeck et al , 2020).…”