Performance and profitability of fungicides for managing soybean white mold: a 10-year summary of cooperative trials
White mold, caused by Sclerotinia sclerotiorum, is a yield-limiting disease of soybean in Brazil. Uniform fungicide trials have been conducted annually since 2009. Data from 74 cooperative field trials conducted over a 10-year period were assembled. We selected five fungicides applied two times around flowering: dimoxistrobin + boscalid (DIMO+BOSC), carbendazim + procymidone (CARB+PROC), fluazinam (FLUZ), fluopyram (FLUO) and procymidone (PROC). In addition, thiophanate-methyl (TMET) applied four times was included as a low-cost treatment, for comparison. Network models were fitted to the log of white mold incidence (%) and sclerotia mass (g/ha) data and to the non-transformed yield (kg/ha) data for each treatment, including untreated check. Lowest and highest mean (95%CI) percent reduction in incidence and sclerotia mass, from back-transforming the meta-analytic estimates, was 54.2 (49.3-58.7) and 51.6 (43.7-58.3) (TMET) and 83.8 (79.1-87.5) and 87 (81.9-91.6) (CARB+PROC), respectively. The overall mean (95%CI) yield responses ranged from 323 (247.4 - 400.3) kg/ha (TMET) to 626 (521.7-731.7) kg/ha (DIMO+BOSC), but the variance was significantly explained by a binary variable (30% threshold) describing disease incidence in untreated check. On average, an increment of 352 kg/ha was estimated for trials where incidence was >30% compared to low-disease scenario. Hence, the probability of breaking even on fungicide costs for high-disease scenario was greater than 65% for the more effective, but more expensive (FLUZ) fungicide than TMET. For the low-disease scenario, profitability was less likely and depended more on variations in fungicide cost and soybean price.