Wet Brazil soy belt may face more Asian rust

By Reese Ewing

SAO PAULO (Reuters) - Brazilian soybean producers may have a tougher battle against Asian rust this season as above-average rains are likely to yield a record crop but also provide an inviting home for the fungus, a plant pathologist said on Thursday.

Rafael Moreira Soares, the soy rust specialist at the government's crop research company Embrapa, told Reuters that it was still early in the season to know how the disease -- which can destroy 80 percent of a soy field if left untreated -- would behave under the weather conditions going forward.

"That said, all indications appear to point to greater problems with rust this year," Soares said. "El Nino looks to be having an affect. Brazil's grain belt is wetter and this is good for spreading rust."

In the 2008/09 soybean season, dry weather curbed output from Brazil's crop but also kept losses to rust down.

But Brazil's soy belt has been wetter than normal this planting season (Sept-Dec) and the region is entering the December-February rainy season. No. 2 soybean state Parana is already behind in planting because rains have been too strong for farmers to enter fields to sow the new crop.

Soy rust first appeared in Brazil in 2001 on a couple farms in the south, then quickly spread across almost the entire country. In the worst years, around 2003 through 2005, Brazil was losing more than 4 million tonnes of soy a year to rust.

Farmers are much better prepared now to deal with rust using fungicides, but if rains persist producers will be unable to put up a fight by spraying. There are years when it can rain for three or four weeks straight in Brazil's center-west, and that has proved disastrous for controlling rust.

The government has in past years prohibited producers from planting soybeans over the winter months of June to September, to reduce the spread of rust from one season to the next. The policy has been relatively successful. Rust outbreaks have been much more limited in number since the policy started, but it is not foolproof.

"Farmers have been careless in cleaning up the so-called voluntary soy that crops up around fields from spilled beans over the winter months," said Soares. "This soy serves as a host to carry the disease over into the next season."

He said the signs of rust would not begin to show up in force until the soy crop begins to flow. As plants divert more energy to bean production, their natural defenses weaken and rust can easily set in. Flowering will begin in early December in some places.

Brazil is forecast to harvest a record crop of around 64 million tonnes of soybeans this year, up from around 57 million in 2008/09.

Soares said that producers had on average enough fungicide for two sprays on the farm or at the cooperative ready for use. In years when outbreaks of the disease are particularly bad, producers can spray as many as five times to control rust.

"There is a risk with producers' trying to keep costs down that they will not have sufficient fungicide on hand," said Soares. "If rust shows up, you need to spray immediately. If producers have to order the chemicals after rust appears, it will be too late."