August 21, 2012
Early Onset of Soybean Rust Possible in Mato Grosso
Scientists in Mato Grosso are very concerned that live spores of soybean rust will be present in the state as soon as the 2012/13 soybean crop is planted. The reason why they are concerned is because of the extraordinary amount of volunteer soybean plants that have survived the 90-day soybean free period when all volunteer soybeans are supposed to be destroyed. Scouts have found live plants along the state's highways, around urban areas, in soybean fields, and next to transportation and storage facilities and 100% of the plants have been found to be infected with soybean rust.
The reason why there are so many volunteer soybeans this year is because the rains continued to fall until the end of June allowing for the spilled seeds to germinate over the last few months. Normally, the rains end by early May and it is too dry for the seeds to germinate after that point, not so this year.
Rust spores can remain viable for up to four weeks without a host plant being available. Even if an infested plant dies, the spores can survive for up to four weeks on the dried leaves. Scientists are urging property owners to destroy as many of the live soybeans as possible by either burying the plants or putting them in plastic bags that are securely tied. At this point it is impossible to destroy all the soybean plants especially those along the highways. The new soybean crop in the state could start to be planted within 25 days, so there is a near certainty that live spores will be floating around at the same time the new crop germinates.
With the potential for an early onset of soybean rust, farmers in the state may have to start spraying their fields earlier than they normally would. In a good year, they may be able to put off the first application of fungicides until December. In a bad year, they may have to start applying fungicides in October or November. It remains to be seen what type of year 2012/13 will end up being.
The 2011/12 growing season was one of the worst years for soybean rust in Mato Grosso. Estimates are that 800,000 tons of potential production was lost due to the disease. Since the discovery of soybean rust in Brazil in the early 2000's it has cost the Brazilian agricultural economy an estimated US$ 19.7 billion in chemical costs and lost production.