South America Calling

SAO PAULO, Brazil (DTN) -- Brazilian farmers appear to have done a good job controlling the dangerous Asian soybean rust fungus so far this season.

Despite wet weather providing ideal conditions for the fungus in Mato Grosso and environs, close monitoring and timely spraying have generally limited rust's spread.

So with 37% of Brazil's record crop harvested, farmers have reported just 419 cases, according to the Anti-Rust Consortium, a public-private partnership set up to monitor the fungus.

While this year's figure is higher than the 260 cases registered at the same point last year, when drought hampered the fungus' spread, it's much lower than the 704 cases registered at the same point in 2010-11 and the 2,325 cases reported in the period for 2009-10.

"Farmers have taken great care this season and we have managed to control the rust effectively," said Luiz Nery Ribas, technical director at the Mato Grosso Soybean and Corn Growers Association (APROSOJA).

Close monitoring for rust has become the norm in Mato Grosso, Brazil's No. 1 soy state, where farmers sprayed fungicide an average of 2.5 times this season, he explained.

The rust fungus, or Phakopsora pachyrhizi, spreads and intensifies throughout the season, reaching its nadir at around harvest time.

"We will certainly see the number of cases increase rapidly from now on as harvesting throws the pollen in the air. But the fact that we have controlled it so far is positive," said Ribas.

The fungus causes lesions on the leaves of soybean plants, which impede the formation of the bean and can result in massive yield losses. In more extreme cases, the fungus can kill the plant.

However, it is too early for farm leaders to hail anti-rust measures as an unreserved success with growth in the cases of rust in the south causing concern.

Normally, the center-west regions lead the rankings because of the wet conditions and because they harvest earlier. But, this year, the southern state of Parana heads the rankings with 110 cases, followed by neighboring Rio Grande do Sul with 105 cases. Mato Grosso, in the center-west, trails in third with 90 cases.

The fungus' early appearance in the south is a concern as the region harvests later and so the bean plants are exposed for longer. Indeed, Rio Grande do Sul hasn't started harvesting yet.

Alastair Stewart can be reached at alastair.stewart@telventdtn.com

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