Soybean patch showing brown spots
In the agricultural world, maintaining healthy soybean crops is crucial for farmers and the industry as a whole. One significant threat to soybean production is Septoria Leaf Spot, also known as Brown Spot, caused by the fungus Septoria glycines. This disease primarily causes early defoliation of lower leaves in soybeans, potentially leading to yield losses ranging from 2 to 4 bu per acre.
Symptoms of Brown Spot appear first on the cotyledons and unifoliate leaves early in the growing season, with angular, red to brown spots on both upper and lower leaf surfaces. As the disease progresses, leaves with numerous spots rapidly turn yellow and fall to the ground as defoliation proceeds from the bottom of the plant toward the top. In severe cases, irregular brown lesions with indefinite borders may also develop on infected pods, stems, and petioles.
Effective management strategies for Brown Spot involve an integrated approach combining cultural practices, genetic resistance, and fungicide use. Accurate diagnosis and scouting are crucial first steps to identify the disease and apply the most appropriate management tactics during the growing season.
Cultural practices play a vital role in disease control. High-quality seeds with resistance to diseases should be planted to reduce the risk of infection. Improving soil drainage and avoiding low-lying areas prone to moisture accumulation can also help prevent Brown Spot. A good seedbed should be prepared when no-till is not practiced, and seeds should be planted at the proper depth to promote healthy growth. Herbicide injury to seedlings should be avoided to maintain plant health. Removing or managing crop residues that harbor pathogens can reduce inoculum and help prevent disease spread.
Genetic resistance is another essential aspect of Brown Spot management. Selecting soybean varieties with resistance or partial resistance to Septoria Leaf Spot where available helps reduce disease severity.
Fungicide programs are effective in controlling Brown Spot when weather conditions favor disease development. However, to prevent resistance development, best practices include employing integrated pest management (IPM) to reduce reliance on fungicides, alternating and mixing fungicides with different modes of action, monitoring fungal populations to detect and manage resistance development, and considering additions such as sulfur in fungicide sprays to enhance control efficacy.
If replanting is necessary due to seedling diseases, seed treatments with fungicides targeting specific fungi can reduce further problems.
By integrating these strategies—cultural controls, resistant varieties, and careful fungicide use—farmers can effectively manage Septoria Leaf Spot in soybean crops, protect yields, and ensure sustainable disease control.
For more information, visit Your Local Extension Office at extension.osu.edu/locate-an-office or The Ohio State University Department of Plant Pathology at oardc.ohio-state.edu/ohiofieldcropdisease. It is essential to remember that the spread of the fungus is usually halted during hot, dry weather, and that managing Brown Spot disease is rarely economically feasible without the implementation of these integrated strategies. Figure 2 shows levels of Septoria Brown Spot, and Figure 3 displays Septoria Brown Spot Ratings (Percent Leaf Area Affected).
In the realm of health-and-wellness, understanding and managing Septoria Leaf Spot in soybean crops holds similar importance as maintaining human health. The integrated approach of cultural practices, genetically resistant varieties, and careful fungicide use can serve as a preventive healthcare strategy, ensuring yields and sustainable disease control, much like a balanced diet and regular exercise contribute to human health.
