Performance and Profitability of Fungicides for Managing Soybean White Mold: A 10-Year Summary of Cooperative Trials

Abstract

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: dimoxystrobin plus boscalid (DIMO+BOSC), carbendazim plus procymidone (CARB+PROC), fluazinam (FLUZ), fluopyram (FLUO), and procymidone (PROC). For comparison, thiophanate-methyl (TMET) applied four times was also included as a low-cost treatment. Network models were fitted to the log of white mold incidence (percentages) and log of sclerotia mass data (grams/hectare) and to the nontransformed yield data (kilograms/hectare) for each treatment, including the untreated check. Back-transformation of the meta-analytic estimates indicated that the lowest and highest mean (95% confidence interval [CI]) percent reductions in incidence and sclerotia mass were 54.2 (49.3 to 58.7) and 51.6% (43.7 to 58.3) for TMET and 83.8 (79.1 to 87.5) and 87% (81.9 to 91.6) for CARB+PROC, respectively. The overall mean (95% CI) yield responses ranged from 323 kg/ha (247.4 to 400.3) for TMET to 626 kg/ha (521.7 to 731.7) for DIMO+BOSC, but the variance was significantly reduced by a binary variable (30% threshold) describing disease incidence in the untreated check. On average, an increment of 352 kg/ha was estimated for trials where the incidence was >30% compared with the low-disease scenario. Hence, the probability of breaking even on fungicide costs for the high-disease scenario was >65% for the more effective, but more expensive fungicide (FLUZ) than TMET. For the low-disease scenario, profitability was less likely and depended more on variations in fungicide cost and soybean price.

Performance of dual and triple fungicide premixes for managing soybean rust across years and regions in Brazil: A meta‐analysis

“…Accordingly, more profitable scenarios were calculated for the SE region. The increased levels of yield return that occurred under high disease severity conditions is in agreement with the effect of fungicides on soybean diseases found in previous studies, suggesting greater benefit with increased disease pressure (Barro et al, 2019; Delaney et al, 2018; Edwards‐Molina et al, 2018).…”

“…Hence, further analyses that combine multiple season data and focus on estimating not only the means, but also the uncertainty and factors explaining variation, may provide additional insights into the disease management strategy. Meta‐analysis has become standard in plant pathology to summarize the effect of treatments on plant disease management (Barro et al, 2019; Edwards‐Molina et al, 2018; Machado et al, 2017; Scherm et al, 2009) including effect of year on both fungicide efficacy and yield response over time (Dalla Lana et al, 2018).…”

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

“…The presented relationship between efficacy and yield increase is intrinsically dependent on knowledge gathered in previous studies on the soybean rust severity and yield relationship (Dalla Lana et al, 2015). In fact, a positive association between control efficacy and yield response to fungicides has been suggested in flowering diseases of wheat (Machado et al, 2017) and soybean (Barro et al, 2019). For soybean rust, the relationship has been established for many fungicides with varying efficacy and yield response (Dalla Lana et al, 2018).…”

“…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).…”

Temporal and regional performance of dual and triple premixes for soybean rust management in Brazil: A meta-analysis update

“…Their original intent is not to base a regional recommendation of fungicide program because sequential sprays of the same fungicide are tested in late season planted crops; the former practice is not encouraged due to fungicide resistance issues (Hollomon 2015) . Data from these trials shall serve to define programs of controls considering the sowing date and disease occurrences since trials are also carried out for other soybean pathogens (Edwards-Molina et al 2018;Barro et al 2019). In addition, data can be used to compare and monitor fungicide performance over time and space (Dalla Lana et al 2018) .…”