| Resumo: |
Soybean {Glycine max) is currently the most widely grown and rapidly expanding crop in Argentina, and brown spot caused by Septoria glycines is a major foliage disease that affects this crop. Triáis in the 2005 and 2006 growing seasons were undertaken using soybean (Glycine max) cv. Nidera A4800 RR. A randomized complete block design was used with four replicates. Two biological fungicides, based on Bacillus subtilis or B. pumilus, and four conventional fungicides, pyraclostrobin in combination with epoxiconazole (Opera 25 SC, BASF Argentina), azoxystrobin (Amistar 25 SC, Syngenta Argentina), trifloxystrobin in combination with cyproconazole (Sphere 267,5 EC, Bayer, Argentina), and tebuconazole (Folicur 25 EC, Bayer, Argentina), were evaluated. Fungicides were applied at the R3 stage of soybean development. The effectiveness of the fungicide was determined by measuring disease incidence and severity High doses of biological fungicides and all chemical treatments reduced the incidence of disease compared to the untreated control, but only Bacillus subtilis QST 713 at a high dose showed a similar efficacy for reducing disease severity. The best results for reducing disease incidence and severity were obtained with the strobilurin fungicides pyraclostrobin plus epoxiconazole, trifloxystrobin plus cyproconazole, and azoxystrobin. The best yields were obtained with chemical and biological treatments at high doses applied at R3; these treatments appeared to have a direct relationship with reduced development of foliar symptoms.
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