02482naa a2200181 a 450000100080000000500110000800800410001910000170006024500790007726000090015630000110016549000370017650001800021352016280039370000160202170000170203777302460205414667592007-07-27       2004    bl uuuu     u00u1 u    #d1 aSILVA, J. C.  aOccurrence of Asian Soybean Rust on irrigated fields in Maranhão, Brazil.  c2004  ap. 85.  a(Embrapa Soja. Documentos, 228).  aEditado por Flávio Moscardi, Clara Beatriz Hoffmann-Campo, Odilon Ferreira Saraiva, Paulo Roberto Galerani, Francisco Carlos Krzyzanowski, Mercedes Concordia Carrão-Panizzi.  aThe Asian Soybean Rust (ASR) caused by the fungus Phakopsora pachyrhizi is the most important disease in Brazilian soybean production currently. First reported in 2001 in South America, the disease spread to many Brazilian fields in 2003, with a potential of yield reductions up to 75%. In the state of Maranhão, Northeast Brazil, it occurred at harvesting time of the 2003 growing season, causing no damages. At irrigated fields for seed production in the municipalities of Balsas and Riachão, during the period from May to October, it was observed some incidence of ASR, with different levels of severity. Farmers adopted chemical control as soon as the disease were observed in the field, spraying fungicides like Pyraclostrobin+Epoxiconazole, Tebuconazole, Difenoconazole and Azoxystrobin. Disease severity was estimated as perceptual of infected leaf area (i.l.a.). The plant development stage and the weather conditions were also registered. For diagnosis confirmation, the presence of uredia and urediniospores were checked with stereomicroscope on samples of leaves hold in humid chamber for 24 hours at room temperature. Late chemical control resulted in high disease severity rates on soybean cvs. BRS Jiripoca (40% i.l.a.), BRS Sambaiba (25% i.l.a.) and DM Nobre (25% i.l.a.). Preventive control shows low severity rates on cvs. BRS Tracaja (5% i.l.a.), BRS Uirapuru (2% i.l.a.), BRS Pati (1% i.l.a.), BRS Pintado (1% i.l.a.) and BRS Pirarara (1% i.l.a.). An increase on ASR severity was observed about 5 days after a rainy day of 15mm. The air temperature varied from 21ºC to 35ºC during the growing season.1 aMAIA, G. L.1 aMEYER, M. C.  tIn: WORLD SOYBEAN RESEARCH CONFERENCE, 7.; INTERNATIONAL SOYBEAN PROCESSING AND UTILIZATION CONFERENCE, 4.; CONGRESSO BRASILEIRO DE SOJA, 3., 2004, Foz do Iguassu. Abstracts of contributed papers and posters. Londrina: Embrapa Soybean, 2004.