Researcher warns of challenges in managing soybean diseases in the 2023-24 harvest

In the search for high yields in the 2023/24 harvest, farmers faced significant challenges in controlling soybean diseases, as highlighted by RTC/CCGL Phytopathology researcher, Carlos Pizolotto. In his analysis, the researcher outlined the challenges encountered and the measures necessary to face them, highlighting the importance of preventive action and constant monitoring.

One of the main concerns was the impact of different weather conditions, characterized by above-average rainfall volumes. Although these rains boosted yields, they also increased the incidence of diseases, especially Asian rust, still the main threat to soybean crops. Compared to the 2000s, marked by the first epidemics of the disease in Brazil, the current harvest witnessed one of the greatest pressures of Asian soybean rust.

In addition to rust, the early appearance of leaf spots, the incidence of anthracnose, and the emerging Diaporthe/Phomopsis complex, which results in stem breakage and pod anomalies, were other points presented by the researcher. To face these challenges, the need for preventive management is emphasized, starting pesticide applications earlier in the season and adopting an integrated approach.

According to the researcher, application at the V3-V4 stage (between 20 and 25 days after crop emergence) is important, as it is crucial for effective disease control, especially leaf spots and anthracnose. He also highlighted the effectiveness of the combination of chemical and biological products, such as Bacillus-based biofungicides, which have demonstrated a significant increase in disease control, including Asian rust.

Another critical aspect addressed was the adequate rotation of products, aiming to avoid resistance and ensure the continued effectiveness of pesticides. The researcher highlighted the importance of regular application intervals and the use of carboxamides and triazoles, associated with protectants, to maximize effectiveness and prolong disease control throughout the crop cycle.

It is also necessary to pay attention to end-of-cycle applications, especially for those who started fungicide applications late or in scenarios of greater disease pressure. The researcher warned of the importance of avoiding excessive repetition of curative products, such as prothioconazole and tebuconazole, which can cause phytotoxicity, especially at the end of the cycle.

"The introduction of morpholine brought an important curative action," he added. He also highlighted the effectiveness of rotating some triazoles, such as cyproconazole, in end-of-cycle applications. Furthermore, he mentioned the importance of using increasing doses of multisite products, such as mancozeb and chlorothalonil, for more effective disease control. "Those who worked with increasing doses of the protector had greater success in controlling these diseases," he said.  

Another point addressed by Pizolotto was the issue of the interval between applications. He highlighted the importance of the application interval, shorter intervals, especially in later sowing or in off-season soybeans, were more effective in controlling diseases. This is because shorter intervals are more effective in reducing inoculum production of disease-causing fungi in soybeans.

Furthermore, he emphasized the need to properly manage crop residues and adopt crop rotation practices to reduce disease pressure, especially in the case of the seed-borne Diaporthe complex present in crop residues. The use of effective biofungicides and seed treatments was also highlighted as an essential part of integrated disease management.

In short, the 2023/24 harvest presented significant challenges in the management of soybean diseases, but also highlighted the effectiveness of preventive and integrated strategies. Pizolotto's warning highlights the importance of adopting proactive measures and continuous monitoring to guarantee the health and productivity of soybean crops in Brazil.