Soybean pod and grain rot: advances in knowledge about the disease.

Soybean pod and grain rot has been causing losses to producers since the 2018/2019 harvest, especially in the state of Mato Grosso, affecting grain quality and crop productivity. The symptoms of the fungal disease, caused by species of the genera Diaporthe and Fusarium, which cause various diseases in the crop, begin to appear at the beginning of grain filling (R5 stage), and include pod and grain rot, with severities varying between harvests, environments, and cultivars.

Since the disease appeared, Embrapa and its partners have been conducting studies to understand and manage it. The main actions are being developed regarding the evaluation of cultivars, sowing times, and fungicide management.

The region most affected by pod rot has been the Mid-North of Mato Grosso. However, in the 2025/2026 agricultural year, the western region of the state, which includes the municipalities of Campo Novo do Parecis and Tangará da Serra, has been showing extensive areas with the disease. This fact reveals that pod and grain rot is reaching new areas and that research should continue and be extended to these agricultural regions.

New results from cultivar evaluation and fungicide management were presented by Embrapa and partners in the publications “Evaluation of cultivars and sowing times for reaction to soybean grain rot – second year of evaluation, 2023/2024 crop” and “Efficacy of fungicides for the control of pod and grain rot in soybeans, in the 2025/2026 crop: Summarized results of cooperative trials”, which can be downloaded for free.

The first publication reports on a study conducted in the 2023/2024 growing season in Mato Grosso, encompassing the evaluation of 26 genetically modified soybean cultivars and four conventional soybean cultivars regarding their reaction to pod and grain rot, as well as evaluating the incidence of the disease at three different sowing times with three cultivars, since soybean productivity in Mato Grosso is known to be influenced by the sowing time. The cultivar evaluation experiments were conducted in four locations: two in Sinop, one in Sorriso, and one in Lucas do Rio Verde; and the sowing time experiments were conducted in Nova Mutum and Lucas do Rio Verde.

The study revealed significant differences between cultivars regarding resistance to pod rot. The incidence of the disease was higher in late sowings, resulting in lower grain productivity at those times. The results obtained are relevant for crop planning by producers, as they indicated that choosing cultivars with good levels of resistance, combined with early sowing times, can help minimize the impacts of pod and grain rot.

However, continuous evaluation of these cultivars for their reaction to the disease is fundamental for determining management. Similarly, a greater number of evaluations is necessary to eventually define the best sowing time, since the occurrence of pod and grain rot in soybeans is influenced by environmental conditions that can vary over the years.

The second publication presents the results of 13 experiments conducted in the 2025/2026 growing season by research institutions in Mato Grosso and Rondônia, covering areas with a history of soybean pod and grain rot, to evaluate the effectiveness of fungicides in controlling the disease. Site-specific fungicides (which attack a single protein or enzyme in the fungus's metabolism) were evaluated in combination with multi-site fungicides (which attack several vital points of the fungus at the same time), as well as isolated active ingredients.

A reduction in the incidence of pod and grain rot symptoms and an increase in productivity were observed with different fungicides, as a consequence not only of the reduction of these symptoms but also of the control of target spot and late-cycle soybean diseases. The study results therefore reinforce the importance of adopting fungicide programs as a management strategy, which should be integrated with other practices in the evaluated region, considering the sensitivity of the cultivars, environmental conditions, and the simultaneous occurrence of other diseases.

It is important to note that the relevant knowledge generated by these studies does not represent direct management recommendations, as the research requires further evaluation. However, as a general recommendation, producers should diversify the cultivars used to reduce the risk of decreased productivity due to diseases and other adverse factors. For the control and management of soybean pod and grain rot, it is essential to consider the reaction of the cultivars, as well as to adequately define sowing dates and adopt chemical control strategies that prioritize the rotation of fungicides with different modes of action, avoiding consecutive applications of the same fungicide to reduce the selection pressure for fungal resistance to the products.

*Per Austeclínio Lopes de Farias Neto, researcher at Embrapa Cerrados