Recent research has evaluated how target spot, caused by the fungus Corynespora cassiicola, will affect soybean productivity in Brazil under different climate scenarios until the end of the century. The study reveals that, although climate change tends to increase soybean productivity in all regions evaluated, the severity of the disease is expected to increase until 2039, and then decrease until 2100. This phenomenon is directly linked to the increase in temperature and the concentration of carbon dioxide (CO2) in the atmosphere.
The researchers used a dynamic epidemiological model coupled with the DSSAT/Cropgro-Soybean agricultural simulation model. This method allowed the simulation of plant-pathogen interactions in different climate scenarios, considering the main factors that affect soybean development and diseases. The regions analyzed were the North, Center and South of Brazil, which together represent the largest soybean production areas in the country.
The results indicate that soybean production is expected to increase under all climate scenarios. However, the severity of target spot will follow a pattern of increase until 2039, followed by a gradual decrease until 2100. The most stable scenario was SSP1-RCP2.6, considered the most optimistic, with the smallest decrease in production. In contrast, the most pessimistic scenarios, such as SSP3-RCP7.0 and SSP5-RCP8.5, point to a greater reduction in productivity due to the impact of high temperatures and high CO2 levels.
The research highlights that the increase in temperature, especially between 2020 and 2039, creates favorable conditions for the spread of the fungus, which reaches its maximum development potential at temperatures around 25°C. After this period, the increase in temperature begins to inhibit the progression of the disease, especially with the increase in average temperatures that exceed 32°C.
Another important point discussed in the research is the compensatory effect of the increase in CO2 in the atmosphere. This factor tends to favor the increase in soybean leaf mass, reducing the severity of the disease, since, proportionally, the pathogen affects a smaller area of the leaves. In addition, the shortening of the soybean cycle, caused by the increase in temperature, can anticipate the growth stages of the plant, making it more vulnerable to pathogen attacks.
The study also raises questions about climate change adaptation in soybean management. The authors suggest that selecting varieties with longer cycles, combined with adjustments to the planting calendar and earlier application of fungicides, are effective strategies to mitigate disease risk. Changes in fungicide application techniques will also be necessary to ensure effective penetration through the denser canopies caused by increased plant biomass.
Finally, the study highlights the importance of considering the variability of future rainfall in Brazil. The country is expected to experience more frequent periods of drought, followed by heavy rainfall, which could directly impact the development of fungal diseases. The increased duration of moisture on leaves, caused by more intense rainfall, could favor the germination of fungal spores.
The research concludes that despite the increase in soybean productivity, the evolution of target spot severity and climate change represent significant challenges for Brazilian agriculture. Management and adaptation strategies, such as the selection of appropriate varieties and the review of fungicide application techniques, will be crucial to ensure the sustainability of soybean production in the future.
Full material can be read at doi.org/10.1016/j.eja.2024.127361
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