Brazil MAPA recognizes "Crazy Soy II" as new soybean disease‏

The disease known in Brazil as Soja Louca II (or Crazy Soy II in English) was recognized by the Ministry of Agriculture, Livestock, and Supply (MAPA) and the cause was the Aphelenchoides sp. nematode. Ten years ago, researchers and partners from Brazilian Agricultural Research Company (Embrapa) worked on the identification of the Crazy Soy, but only in 2015 the causing agent was identified. Since the 2005/2006 crop season, the disease has generated reductions of up to 60% on soybean yields, mostly in warm and rainy regions in states such as Maranhão, Tocantins, Pará, and Mato Grosso.

 

The main symptoms of Crazy Soy II are observed at the reproductive stage of soybeans which presents tapering of leaves on the top of the plants, leave corrugation and thickening of the veins. Besides, the leaves with symptoms present darker coloration and less hairiness compared to the regulars. It is also observed that the rods show deformation and thickening of the ties. The green beans can show injuries, cracks, rotting, and the reduction of the number of grains.

 

For researcher Maurício Meyer of Embrapa soybean unit, after the diagnosis, the next step is to detail the management actions to guarantee the control of the disease. "The identification of the causing agent represents an important breakthrough because it directs the research activities towards the definition of management strategies, which will bring a huge breath to producers that faced losses because of a then unknown disease," reveals the Embrapa researcher.

 

During the studies made in 2011, researchers already had proven that the Crazy Soy II was not caused by viruses or mites. However, only in this year, the isolation and the multiplication of a nematode at a laboratory was possible to identify the causing agent of this disease.

 

Maurício Meyer inoculated healthy soybean plants with different concentrations of Aphelenchoides sp. at different development stages of the crop. After 12 days, the scientist observed that the plants started to show symptoms of the disease. "These sick plants were send to the lab and we found that a significant quantity of the nematode which proving that the nematode triggers the disease," explains Meyer.

 

As soybean cultivars tolerant to Crazy Soy II are not known, Embrapa recommends an adequate crop and soil management to avoid contamination. "We indicate dissection anticipated to the soybean seedling and an effective invasive plants control immediately after the emergence of the soy," concludes Maurício Meyer.