Soybean (Glycine maxL.) Response to Fungicides in the Absence of Disease Pressure

Abstract

Field studies were conducted during the 2010 and 2011 growing seasons along the Texas Upper Gulf Coast region to study the effects of fungicides on soybean disease development and to evaluate the response of four soybean cultivars to prothioconazole plus trifloxystrobin and pyraclostrobin. In neither year did any soybean diseases develop enough to be an issue. Only NKS 51-T8 responded to a fungicide treatment in 2010 while HBK 5025 responded in 2011. Prothioconazole plus trifloxystrobin increased NKS 51-T8 yield by 23% in 2010 while in 2011 the yield of HBK 5025 was increased 14% over the unsprayed check. No yield response was noted with pyraclostrobin on any soybean cultivar. Only prothioconazole + trifloxystrobin applied to either NKS 51-T8 or DP5335 in 2010 resulted in a net increase in dollars per hectare over the unsprayed check of the respective cultivar. In 2011, under extremely dry conditions, all fungicides with the exception of prothioconazole + trifloxystrobin applied to HBK 5025 resulted in a net decrease in returns over the unsprayed check.

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

“…At relatively low disease pressure (target spot severity at R5–R6 ≤ 35%), the highest yield response was observed with the application of PROT_TRIF; however, the only fungicide that paid the application costs (based on the costs and prices considered here) was CZM, the cheapest of the tested products. A similar trend was observed in a set of fungicide experiments in growers’ fields in Texas (USA) in the absence of disease pressure (Grichar, ). Of the fungicide programmes tested, the mixture PROT_TRIF (sprayed at R3 + R5) was the only treatment to result in significant yield increments of 23% and 14% in 2010 or 2011, relative to the nontreated control.…”

“…Of the fungicide programmes tested, the mixture PROT_TRIF (sprayed at R3 + R5) was the only treatment to result in significant yield increments of 23% and 14% in 2010 or 2011, relative to the nontreated control. However, net increase in dollars per hectare over the nontreated control was only observed in two out of eight experiments (Grichar, ). In another trial under low disease pressure, no changes in leaf area index, dry matter, respiration, transpiration, stomatal conductance, leaf temperature, number of pods or weight of 1000 seeds were observed in response to the application of fluxapyroxad alone or in combination with pyraclostrobin (Carrijo, ).…”

Yield losses of soybean due to target spot (<i>Corynespora cassiicola</i>), its genetic and chemical management

“…At low disease pressure context, the highest yield response was observed with the application of PROT_TRIF, however the only fungicide that paid the application costs for the current economical context was carbendazim. Similar trend was observed in a set of fungicide experiments at growers' fields in Texas (USA) under absence of disease pressure: the mixture prothioconazole + trifloxystrobin (sprayed at R3 + R5) was the only fungicide product tested that reported significant yield increments of 23% and 14% in 2010 or 2011 relative to the same cultivar without the fungicide, however net increase in dollars per hectare over the unsprayed check was only observed in 2 out of 8 experiments (Grichar 2013). On the other hand, no changes in leaf area index, dry matter, respiration, transpiration, stomatal conductance, leaf temperature, number of pods or weight of 1000 seeds were observed for the treatment fluxapyroxad, neither alone nor in combination with pyraclostrobin in a non-diseased experiment (Carrijo 2014).…”

Effect of Fungicide Applications on Grain Sorghum (Sorghum bicolor L.) Growth and Yield

“…Swoboda and Pedersen [31] noted, in a 2-year study on soybean, that fungicides had no effect on yield. Grichar [15] noted that the use of fungicides on soybean along the upper Texas Gulf Coast under little or no disease pressure resulted in few increases in yield and subsequent increases in net returns. In several instances, the use of fungicides resulted in a decrease in net returns, especially in a year with below normal rainfall.…”

“…Three of the newer fungicides labeled for use in grain sorghum are azoxystrobin, flutriafol, and pyraclostrobin. Azoxystrobin and pyraclostrobin are strobilurin-type fungicides that have shown activity against many different fungal pathogens in soybean (Glycine max L.), peanut (Arachis hypogaea L.), and various other crops [15][16][17][18]. Pyraclostrobin is rapidly absorbed by leaf tissue and has demonstrated translaminar movement through layers of the leaf; however, the material is not redistributed throughout the plant like a true systemic fungicide [9,19].…”