Feb 18, 2022

Unknown Pathogen Responsible for Soy Seed Rot in Mato Grosso

Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.

For three consecutive growing seasons, soybeans grown in the mid-north region of Mato Grosso, Brazil have been negatively impacted by a disease that causes the seeds to rot inside the pods. At this point, scientists have not been able to identify a specific pathogen connected with this anomaly.

Recently a group of researchers led by Embrapa Soja (Embrapa Soybeans) and the Foundation to Aid Agriculture and Livestock Research in Mato Grosso (Fundacao-MT) met with other institutions, specialists, and producers in Mato Grosso to access the scope of the damage and potential causes.

The group estimates that the anomaly impacted approximately 2.5 million hectares of soybeans in Mato Grosso this growing season (6.17 million acres) in various degrees of intensity. Farmers in the region reported that the disease resulted in lower soybean yields and that as much as 40% of the soybean seed had rotted in the pods.

Researchers that examined the affected seed found that various fungus such as Fusarium, Colletotrichum, Phomopsis, Cereospors, and various bacteria were present, but not to the extent that would cause widespread damage. These are considered opportunistic pathogens that emerge when environmental conditions are favorable and they are common and widespread in soybeans and generally controlled by traditional fungicide treatments.

Scientists are wondering if the cause of the anomaly is a new species or if a known pathogen has mutated to such an extent that the fungicide treatments are no longer effective. They speculate that there could also be a genetic connection that could make some of common soybean varieties grown in the area more susceptible to the disease.

They conducted a series of experiments during the last two growing season utilizing different planting dates, soybean varieties and fungicide treatments to try to identify the problem. The used three different planting dates, October 10th, November 1st, and November 11th, two different fungicide treatments, and several soybean varieties.

What they have found thus far is that the problem is more intense for the earliest planted soybeans, but they have not found any specific soybean variety to be more suspectable to the disease. They have also not been able to identify the pathogen responsible for the anomaly.