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TECHNICAL SESSION: Integrated Management of Plant Diseases

Modeling yield losses and risk analysis of fungicide profitability for managing Fusarium head blight in Brazilian spring wheat
Maíra Duffeck - The Pennsylvania State University. Emerson Del Ponte- Departamento de Fitopatologia, Universidade Federal de Viçosa, Paul Esker- The Pennsylvania State University, Franklin Machado- Departamento de Fitopatologia, Universidade Federal de Viçosa, Kaique Alves- Departamento de Fitopatologia,

Fusarium head blight (FHB) is a serious disease of wheat that causes economic losses due to both yield reduction and mycotoxin contamination. A review of the literature on fungicide efficacy evaluated in Brazilian field trials was conducted to obtain FHB-yield data and explore their relationship. Thirty-seven studies (10 years and 11 locations) met the criteria for inclusion in the study (FHB index ? 5% and max-min range ? 4 percent points [p.p.]). Studies were grouped into two production situations: low (Yl< 3631 kg ha-1) or high (Yh > 3631 kg ha-1) yield, based on the median of maximum yields across trials. Population-average intercepts differed between Yl (2,883.6 kg ha-1) and Yh (4,419.5 kg ha-1), but their slopes were similar. The calculated relative yield loss (Dc, damage coefficient) was 1.05 % pp-1 and 1.60 % pp-1 for Yh and Yl, respectively. A crop model simulated attainable wheat yields (no biotic stresses) for 10 planting dates within each year during a 28-year period including prior (1980-1989) and after (1990-2007) FHB resurgence. The predicted losses, from using FHB predictions to penalize attainable yield, were in agreement with literature reports. The probability of not-offsetting (Ploss) the costs (fungicide + application) of one or two sprays of tebuconazole was calculated. For a range of costs (15 to 30 U$/ha) and wheat price (100 to 250 U$/ton) Ploss was higher (> 75%) prior to FHB resurge, regardless the number of sprays, than after 1990.