Soybean rust identified in São Paulo, Brazil

The Antiferrugem Consortium, through the ABC Foundation, made the first record of soybean rust in a commercial area in the 2016-2017 harvest in Taquarituba (São Paulo) on November 15. 

 

ABC Foundation researcher Alan Cordeiro Vaz identified the pathogen while monitoring soybeans sown in September.

 

The first focus on commercial farming was recorded in the 2015-2016 harvest in São Paulo on November 6. Unlike the past harvest, which was under the influence of the El Niño phenomenon that can cause irregular rainfall in the Southeast and Midwest, rainfall delays in the Northeast region and above-average rainfall in the South and climatic conditions tend to neutralize the influence the La Niña phenomenon.

 

Despite the early report of rust, the situation in this crop is still controllable, because the symptoms of the disease are early identified. However, Embrapa researchers explained that in this region of São Paulo, there were several crops that were planted at the end of the sanitary emptiness and they were in an advanced phase of development. Hence, monitoring needs to be intensified in pre-closing or advanced stages of development, and fungicide protection can be initiated, since the presence of the outbreak indicates the presence of spores in the region.

 

Researchers said that rust monitoring and early identification were essential for efficient control. Their suggestion was to carry out the monitoring as quickly as possible, with greater attention to the first planting and places with greater humidity. They suggested collecting leaves from the middle and lower part of the plants and observing them against the light for dark scoring. Rust could be confirmed from the presence of protrusions similar to small wounds or blisters.

 

Soybean rust, caused by the fungus Phakopsora pachyrhizi, is considered the most severe disease of the crop and can cause losses of up to 80% in productivity. The original fungus was reported in Brazil in 2001 and found under favorable conditions for its survival and multiplication throughout the year.

 

According to researchers, the fungus is spread by the wind and can affect any stage of the crop; but due to the accumulation of moisture and the lower incidence of solar radiation in the leaves, the disease tends to begin more commonly after the closing of the canopy.

 

Its introduction has had consequences for the soybean production, and its control is made through the integration of measures such as the adoption of sanitary emptiness (period of 60 to 90 days without soy in the off season) with the objective of reducing inoculum of the fungus. Early cultivars planting at the beginning of the season is recommended to avoid the period of higher incidence of the fungus in cultivars with resistant genes and appropriate use of fungicides.

 

The control of the disease has been threatened by the lower sensitivity of the fungus to the main fungicides, putting at risk the sustainability of the culture. Resistant genes have been incorporated into the cultivars, but the options are still restricted.

 

Embrapa researchers estimate that there are 120 fungicides registered with the Ministry of Agriculture, Livestock and Supply (MAPA) for the control of rust, but their efficiency has been reduced because of the selection of isolates of the fungus which are less sensitive or resistant to them. This enables them to guide the producers to prioritize the use of ready mixtures of different modes of action and the rotation of fungicides to control rust.