Efficiency of foliar fungicides for the control of soybean seed pathogens in Tucumán, Argentina

GONZÁLEZ, V; GÁLVEZ, M R; ALVAREZ, R.S.; FORTINI, L.I.; M DEL CASTILLO,; ZAMORANO, M A; PLOPER, L.D.

Foz do Iguassú

Conferencia; World Soybean Research Conference (VII WSRC).; 2004

Embrapa SOJA y WSRC Continuing Committee

The late season fungal disease complex is now recognized as a major constrain to soybean production in Tucumán and other provinces in northwestern Argentina.  The use of healthy seed is regarded as an important practice to include in management programs for these diseases since all the pathogens included in this complex are seedborne.  The objective of this research was to evaluate the efficiency of foliar fungicides in the control of pathogens present in soybean seed.  Tests were conducted during the 2001/02 and 2002/03 growing seasons in San Agustín, Tucumán, in fields of cultivar A 6401 RG previously cropped to soybean.  Treatments included two fungicides (carbendazim and azoxystrobin) and four fungicide mixtures (difenoconazole + propiconazole, epoxiconazole + carbendazim, pyraclostrobin + carbendazim, and trifloxistrobin + cyproconazole), applied at different growth stages, R3 or R5.4.  The experimental design used in both tests was a randomized complete block design with 4 replications.  Plots consisted of four 6-m rows, spaced 0.5 m apart.  One hundred seeds per plot of the mechanically harvested sample were assayed for seedborne fungi in the laboratory.  Predominant fungi were Fusarium spp., Cercospora kikuchii, and Alternaria spp.  Fusarium spp. was controlled with 50% efficiency when carbendazim was applied at either of the 2 stages. Treatments that included triazoles had an efficiency greater than 50% when applied at R5, and the main control was achieved with the mixture of epoxiconazole + carbendazim.  Among the strobilurins, trifloxistrobin showed the highest control with more than 50% control in R3 applications.  C. kikuchii was controlled with 35% efficiency when carbendazim was applied at either of the 2 stages. Triazoles showed an efficiency of 58.3% in 2001/02 and 56.2% in 2002/03, when applied at R3. When applications were done at R5.4, the control was 41.5% in 2001/02 and 62.5% in 2002/03.  Strobilurins had 44.4% efficiency in 2001/02 and 54.2% in 2002/03 when applied at R3, and 54.2% when treatments were applied at R5.4. The highest levels of control of seedborne C. kikuchii, were obtained with azoxystrobin and pyraclostrobin + carbendazim.  The most efficient treatments for Alternaria spp. control were those that included strobilurins. These treatments showed an efficiency of 68.4% and 67.5% for R3 and R5 applications, respectively.  Triazoles showed 45.1% and 70.4% control when applied at R3 and R5, respectively.  Carbendazim had the lowest levels of Alternaria spp. control (35%).