Meta‐analysis of fungicide efficacy on soybean target spot and cost–benefit assessment

Abstract

Target spot of soybean has spread in Brazil, the southeastern United States and Argentina in the last decade. A collaborative network of field Uniform Fungicide Trials (UFT) in Brazil was created in 2011 to study the target spot control efficacy of fungicides, including azoxystrobin + benzovindiflupyr (AZ_BF), carbendazim (CZM), fluxapyroxad + pyraclostrobin (FLUX_PYRA), epoxiconazole + FLUX_PYRA (EPO_FLUX_PYRA), mancozeb (MZB) and prothioconazole + trifloxystrobin (PROT_TRIF). Network meta‐analysis was used to conduct a quantitative synthesis of UFT data collected from 2012 to 2016 and to evaluate the effects of disease pressure (DP, low ≤ 35% target spot severity in the nontreated control < high) and year of experiment on the overall mean efficacy and yield response to each of the tested fungicides. Based on mean percentage control of target spot severity, the tested fungicides fall into three efficacy groups (EG): high EG, FLUX_PYRA (76.2% control relative to the nontreated control) and EPO_FLUX_PYRA (75.7% control); intermediate EG, PROT_TRIF (66.5% control) and low EG, MZB (49.6% control), AZ_BF (46.7% control) and CZM (32.4% control). DP had a significant effect on yield response. At DPLow, the highest response was due to PROT_TRIF (+342 kg ha−1, +12.8%) and EPO_FLUX_PYRA (+295.5 kg ha−1, +11.2%), whereas at DPHigh, EPO_FLUX_PYRA and FLUX_PYRA outperformed the other treatments, with yield responses of 503 kg ha−1 (+20.2%) and 469 kg ha−1 (+19.1%), respectively. The probability of a positive return on fungicide investment ranged from 0.26 to 0.56 at DPLow and from 0.34 to 0.66 at DPHigh.

Effect of target spot on soybean yield and factors affecting this relationship

“…This yield loss level is within the range of values previously reported for this disease (Koenning et al ., ). The most efficient fungicides to control target spot in the main Brazilian soybean‐growing region were the mixture of fluxapyroxad + pyraclostrobin (from SDHI and QoI chemical groups, respectively) and this same mixture with the addition of the DMI fungicide epoxiconazole (Edwards Molina et al ., ). These mixtures provided up to 75% disease control, with a 19–20% yield increase over non‐treated plots when disease severity was greater than 35%.…”

“…With the third subscript, W ijk and TS ijk now represent yield and disease severity, respectively, for the j th observation of the i th study of the k th level of the covariate; δ k and θ k represent the fixed effect of k th level of the covariate on the intercept and slope, respectively. Six covariates that could potentially affect the relationship between target spot and yield were tested: (i) year of experiment (from 2012 to 2016); (ii) disease pressure as a factor variable (DP: Low < 35% ≤ High) based on mean severity in the non‐treated check (Edwards Molina et al ., ); (iii) baseline yield as a categorical variable (BY Low ≤ studies mean yield = 3300 kg ha −1 < BY High ) based on the mean yield of the most effective fungicide treatment (epoxiconazole + fluxapyroxad + pyraclostrobin) against target spot (Edwards Molina et al ., ); (iv) mean yield response, based on % difference in yield between non‐sprayed check and epoxiconazole + fluxapyroxad + pyraclostrobin fungicide treatment (YR, [(yield Treated − yield Check )/yield Check ] × 100: Low ≤ 10% < High) (Scherm et al ., ); (v) cultivar growth habit (determinate or indeterminate); (vi) soybean cultivar. To evaluate the effect of cultivar on the relationship between target spot and yield, the dataset was reduced to 23 studies, composed of the three cultivars most frequently used in the UFTs: BMX Potência RR ( n = 8), M9144 RR ( n = 8) and TMG8003 ( n = 7).…”

The fungal pathogen Corynespora cassiicola: A review and insights for target spot management on cotton and Soya bean

“…These fungicides are recommended to be used in combination with fungicides with different modes of action, usually a systemic fungicide, to reduce the selection pressure of one fungicide and inhibit the rise of resistant populations (Brent & Hollomon, 2007;FAO, 2012;Ghini & Kimati, 2000). Multisite or protectant fungicides have been employed to control C. cassiicola on tomato fields in Florida, avoiding $3.5 million USD loss (MacKenzie et al, 2018 Molina et al, 2019). From 2014/2015/2017 in Argentina, one and two applications of epoxiconazole + fluxapyroxad + pyraclostrobin were the best treatments to control target spot on Soya bean, with an average control of 59% and 54% compared with the untreated control.…”

“…Since target spot has become a frequent disease in cotton and Soya bean fields, this review aims to gather information to support the disease management programme. We discussed here some disease management strategies to improve and to better understand target spot management, but there is a need of more applied research (Molina et al, 2019). In addition, there is a need for research on developing disease prediction tools to anticipate possible pathogen threats and disease outbreaks (Dutta et al, 2020;Roth et al, 2020).…”

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

“…These large data sets have enabled the use of meta-analytic approaches to study the effects of fungicides on disease control, yield increase and mycotoxin reduction, as well as to explore empirical relationships between FHB index and wheat yield or mycotoxin levels (Madden and Paul 2009;Salgado et al 2011Salgado et al , 2014Salgado et al , 2015. Meta-analysis has become standard for studying empirical relationships between disease and yield data for other diseases like soybean rust (Dalla Lana et al 2015), soybean white mold (Lehner et al 2017) and soybean target spot (Edwards Molina et al 2018).…”