November 27, 2004
Source: Reuters.com [edited]
http://www.reuters.com/locales/c_newsArticle.jsp?type=businessNews&localeKey=es_LT&storyID=6885366

First isolation of Asian fungus in Brazil soybean harvest

The Asian soybean rust [SR] fungus was detected for the first time in the commercial cycle of 2004/2005 (Oct/Sep) of Brazilian soybeans, according to a statement on 22 Nov 2004 by the Brazilian Company of Agricultural Investigation (Embrapa). The outbreak appeared in the municipality of Tres Barras, in Parana state. The soybean crop was planted in Sep 2004.

Previous detection of SR in Brazil had occurred in research areas or in volunteer soybean plants that germinated spontaneously from grains that fell to the ground during the last harvest.

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ProMED-mail
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[The fact that soybeans infected with soybean rust fungus (_Phakopsora pachyrhizi_) have entered the commercial trade in Brazil means that control of SR will become a higher priority in managing the disease. There is no durable resistance to SR. Producers in Brazil will have to increase the applications of chemical fungicides so as to reduce SR inoculum. Assuming that they are registered for use in Brazil, chlorothalonil and azoxystrobin
based fungicides are recommended.

Chlorothalonil based fungicides have provided fair to good rust control in dry beans when applied before infection. Preventative treatment will be critical once SR is actually present. Azoxystrobin based fungicides are in the relatively new strobilurins and are environmentally safer, according to results of foreign trials. Unfortunately, the strobilurins are a single, specific mode of action, so resistance management is a big concern if they are overused or misused. Triazoles will be very important in protecting the strobilurins from rust resistance. Resistance to azoxystrobin has been reported in the United States from 3 powdery mildew isolates.

I thank Pablo Nart <pablo11@hotpop.com> for contributing this piece to ProMED-mail.

Link: <http://www.agweb.com/news_printer.asp?articleID=111783> - Mod.DH]