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December 15, 2010

Crazy Soybean II Worries Soybean Specialists in Brazil

Scientists and farmers in Brazil are joining forces in a concerted effort to try and identify the cause of a relatively new soybean disease they are calling Crazy Soybean II. The anomaly was first identified in the state of Maranhao in northeastern Brazil during the 1996/97 growing season, but at the time it was not considered a significant disease and no economic losses resulted from the disease. Since then, the disease has spread and starting in the 2005/06 growing season, the disease was found primarily in the hotter regions of the cerrado in the states of Mato Grosso, Tocantins, Para, and Maranhao as well as scattered locations in southern Brazil. The disease is now causing economic losses is scattered areas throughout the northern soybean production areas of Brazil.

The disease starts to appear on the average of 50 to 55 days after planting when blemishes start to appear on the stem of the plant. The disease impedes the maturation process of the plant and it results in high rates of flower and pod abortion. If the plant manages to mature, the seeds are small, poorly formed and of lower quality. Researchers are trying to identify the causal organism and if there is an interaction between the disease and management practices such as residue management, chemical applications, and no-till planting. They are hoping to be able to answer some of these questions by the end of the growing season next March or April.

In severe infestations, economic losses from the disease can be as high as 20 to 50% on a localized basis. In northern Mato Grosso, the disease has been present since 2005, but losses were greatest during the last growing season. One farmer in northern Mato Grosso reported that he had two fields of 140 and 130 hectares where the disease caused losses of 30%. His non-affected fields averaged 59 sacks per hectare (3,540 kg/ha or 51.3 bu/ac), but the affected fields averaged 40 and 46 sacks per hectare (34.8 and 40 bu/ac). There also did not appear to be any difference between conventional and genetically modified varieties, they were both equally affected.

The farmer has already checked the same two fields this year and the disease is again present. In one field of 100 hectares, the disease is present on 10 hectares and it will probably continue to spread.

Without knowing what is causing the disease or how to control it, he thinks there is the possibility that Crazy Soybean II could end up being as important as soybean rust (his thoughts). Certainly, the causal organism needs to be identified as quickly as possible and once known, it could take several years to identify successful methods of control. At the present time, the disease is not widespread enough to cause any significant reduction in Brazil's soybean production, but that does not mean that it couldn't become a significant problem in the near future.