Organizing Committee


Poster Presentations


Poster Presentations


Fungicide efficacy for control of Asian soybean rust and Rhizoctonia aerial blight in the northeastern Brazil

Presenter: Mauricio C. Meyer(1)

Other authors and affiliations: Wilson S. Venancio(2), Luis G. Dall’Agnol(2). (1)Embrapa Soybean, Balsas Experimental Station, Balsas, Maranhão 65800-000, Brazil; (2)UEPG - DEFITO, Phytosanitary Department, Ponta Grossa, Paraná 84035-130, Brazil

Since the Asian soybean rust (SBR), caused by Phakopsora pachyrhizi, has reached South America, the estimated losses to Brazilian soybean production through the last six crop seasons has amounted to US$9.8 billion. In the Maranhão State, northeast Brazil, the first 4 years of SBR occurrence caused no appreciable losses, probably due to the unfavorable weather conditions. In the 2007 crop season, SBR caused yield reductions of up to 40% in some fields of Maranhão. Rhizoctonia foliar blight (RFB), caused by Rhizoctonia solani AG1, remains one of the most important soybean diseases in this state. Field trials were conducted in Riachão, Maranhão State, in order to evaluate fungicides in mixed formulations (strobilurins, triazoles, and benzimidazoles) and only triazoles, respectively. The fungicides in these experiments were applied two times: at flowering stage (R2) and at the initial grain formation (R5.1). Among the mixed formulation fungicides, the best control of SBR was observed with trifloxystrobin+tebuconazole, flutriafol+carbendazin, trifloxystrobin+cyproconazole, picoxystrobin+cyproconazole, flutriafol+methyl thiophanate, and azoxystrobin+cyproconazole, which reduced SBR severity by 60.7 to 70.9% when compared with untreated plots (severity of 68.7% of infected leaf area). The best control of RFB was by pyraclostrobin+epxiconazole, trifloxystrobin+propiconazole, and trifloxystrobin+tebuconazole. The grain yield ranged from 2,805 (untreated) to 3,727 kg/ha (pyraclostrobin+epoxiconazole). Among the triazoles, the best SBR control was with tebuconazole and prothioconazole, which reduced SBR severity by 61.5 and 70.3%, respectively. The lowest RFB severities were attained by prothioconazole and tebuconazole. The grain yield within triazoles ranged from 2,878 (untreated) to 3,705 kg/ha (tebuconazole).

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