Rust loses in Mato Grosso may top R$ 1bn in 2011/12

The 2011/12 growing season in Brazil was generally characterized by the drought that impacted the crops in southern Brazil, but soybean producers in Mato Grosso surprisingly suffered losses as well. Their problem was not a lack of rainfall, but rather, excessive moisture that led to one of the most severe outbreaks of soybean rust in the state in recent years. According to the Association of Soybean and Corn Producers in Mato Grosso (Aprosoja), losses from the disease in 2011/12 may end up topping R$ 1 billion in the state.

The main source of the losses is reduced soybean yields caused by the disease. According to the Mato Grosso Institute of Agricultural Economics (Imea), the average soybean yield in the state declined due primarily rust infestations. In 2011/12, the average statewide soybean yield is estimated at 50 sacks per hectare (3,000 kg/ha or 43.5 bu/ac) compared to last year when the statewide yields was 53 sacks per hectare (3,180 kg/ha or 46.1 bu/ac). The rust infestation was worse in the northern part of the state where some yields were reduced by 7-10 sacks per hectare or 6-9 bushels per acre.

Losses from rust this year were greater than any year since the early 2000'Mts when rust first started to appear in the state and farmers and researchers were just learning how to control the disease. Many of the intervening years saw little rust damage in the state, which may have led to farmers feeling that major outbreaks of rust were no longer going to occur.

Researchers feel that some of the factors that led to the increase losses from rust include: excess rainfall during January, extended periods of cloudiness associated with the wet weather, high humidity, difficulty in applying fungicides, a passive attitude on the part of the farmers since rust has not been a major concern for several years, and a potential lack of effectiveness of some products used to control the disease.

Aprosoja is conducting a series of seminars across the state educating its members on the best way to minimize losses from rust. Actions they recommend in the future include: always being alert to the disease in your fields, monitoring the climatic conditions favorable to the spread of rust, closely following technical recommendations on control measures, destroying volunteer soybean plants in the field during the dry season, respect the prohibition period of not growing soybeans between June 15 and September 15, and making all recommended applications of fungicides including the last one prior to harvest. If the disease is not controlled all the way to harvest, the harvesting process can disperse the spores to neighboring fields where the soybeans have not yet started to mature, thus increasing potential losses.