Stem breakage and grain rot are highlights at the Soybean Research Meeting

Amid a harvest marked by uncertainty, soybeans faced problems with stem breakage and grain rot, which have generated misinformation on social media. This was one of the main topics discussed at the Soy Research Meeting, promoted by Embrapa Soja between the 26th and 27th of June, where professor Sérgio Brommonschenkel, from the Federal University of Viçosa (UFV), highlighted the importance of distinguishing between symptoms caused by fungi and those resulting from other factors.

“My main point was to show the different symptoms that have been reported and point out those caused by fungi and those caused by other (non-biological) factors,” said Brommonschenkel during the panel. He explained that while fungi are primarily responsible for grain and pod rot, stem breakage can be attributed to a variety of causes.

Since the 2018/2019 harvest, grain rot has been a recurring problem in the mid-north region of Mato Grosso and Rondônia. Stem breakage, on the other hand, began to be recorded more frequently from the 2020/2021 harvest, also affecting states such as Paraná and Santa Catarina in the current harvest.

Brommonschenkel highlighted that the predominant fungi in cases of rot are species of Diaporthe, Fusarium e Colletotrichum. “These fungi can be found latently in plants and cause symptoms in the final phase of grain filling, in certain climatic conditions”, explained the professor.

Climate plays a crucial role in the incidence of these problems. According to Brommonschenkel, the proximity to the Amazon biome and the greater frequency of rain on BR 163, in Mato Grosso, contribute to excessive humidity at the end of pod filling, creating favorable conditions for grain and pod rot.

Phytopathologist Karla Kudlawiec, from SLC Agrícola, observed that the lower rainfall due to the El Niño phenomenon in the 2023/2024 harvest resulted in a reduction in the incidence of rot. “Since we started trying to identify the causes and management strategies for these problems, we had climate as a determining factor. The presence of wetness at the end of grain filling and maturation is preponderant when it comes to observing symptoms,” said Kudlawiec.

In the states of Mato Grosso and Paraná, important soybean producers, surveys indicated that the area affected by stem breakage was minimal. In Paraná, specifically in the Vale do Ivaí region, the problem was more common in low-lying areas, where temperatures tend to be higher.

Regarding grain rot, Karla Kudlawiec mentioned that it was not possible to evaluate the effectiveness of management strategies due to the low incidence of the problem. “We were unable to assess whether the established management practices, with the rotation of different active ingredients of fungicides, were efficient because there was a low incidence of the problem,” she highlighted.

The panel also addressed the selection of cultivars resistant to stem breakage and grain rot, with the participation of Neucimara Ribeiro, from GDM Genética. “We have already carried out several tests to identify the cause and attempts to select genotypes for the problem. But, as the causes are still not certain, we still need to wait to move forward”, explained Ribeiro.

The research meeting highlighted the continued need for investigations to better understand the causes and develop effective management strategies for these problems, which directly affect soybean productivity in Brazil.