Brown Stem Rot (BSR) primarily impacts soybean-growing regions in the United States and Canada. Its geographic impact is influenced by climate, soil type, and cropping practices.

1. Midwest: BSR is most prevalent in the Midwest, particularly in states like Iowa, Illinois, Minnesota, and Wisconsin. The cooler, moist conditions in these areas during the growing season create an ideal environment for the disease. The heavy, poorly drained soils common in this region also contribute to its prevalence.

2. Great Lakes Region: States and provinces around the Great Lakes, including Michigan, Ohio, and Ontario, are also significantly affected. The humid climate and frequent rainfall in these areas favor the development of BSR.

3. Northern Plains: While less common, BSR can still impact soybean fields in the Northern Plains, including North Dakota and South Dakota, especially in years with cooler, wetter growing seasons.

4. Southern US: BSR is less prevalent in the southern US due to generally warmer and drier conditions, which are less conducive to the disease. However, it can still occur in localized areas with suitable environmental conditions.

5. Canada: In Canada, BSR is primarily a concern in the soybean-growing regions of Ontario and Quebec. The cooler, moist climate in these areas supports the development of the disease.

Understanding the geographic impact of Brown Stem Rot helps in tailoring specific management practices to local conditions, ensuring more effective control and mitigation of damage.

Brown Stem Rot (BSR) typically emerges and impacts soybean fields across the U.S. during the mid to late growing season, particularly from the reproductive stages R3 (beginning pod) to R5 (beginning seed). Here’s a more detailed timeline:

1. Early Season: The fungus Phialophora gregata infects soybean plants early in the growing season, often during the vegetative stages. However, symptoms are not usually visible at this time.

2. Mid to Late Season: Symptoms of BSR become apparent during the reproductive stages, particularly from R3 to R5. This is when the internal browning of the stem tissues and interveinal chlorosis and necrosis on the leaves are most noticeable. The disease thrives in cooler, moist conditions, which are often present during this period in many soybean-growing regions.

3. Environmental Conditions: BSR is more severe in fields with poor drainage or heavy soils that retain moisture. Cool, wet weather during the growing season exacerbates the disease, leading to more pronounced symptoms and greater yield losses.

4. Impact on Yield: The disease disrupts nutrient and water transport within the plant, leading to stunted growth, premature leaf drop, and reduced yields. Yield losses can range from 10% to 30%, depending on the severity of the infection and environmental conditions.

By understanding the timing and conditions that favor BSR, farmers can implement timely management practices, such as crop rotation, planting resistant varieties, and improving field drainage, to mitigate the impact of the disease.

Managing Brown Stem Rot (BSR) in soybeans involves a combination of cultural practices and, to a lesser extent, chemical treatments. Here are specific strategies and examples of products that can help manage BSR:

1. Crop Rotation: Rotate soybeans with non-host crops such as corn, wheat, or small grains. This practice helps reduce the buildup of Phialophora gregata in the soil.

2. Resistant Varieties: Plant soybean varieties that are resistant or tolerant to BSR. Seed companies often provide information on the resistance levels of their varieties.

3. Field Drainage: Improve field drainage to reduce soil moisture levels, as BSR thrives in cool, moist conditions. Practices such as installing tile drainage or using raised beds can help.

4. Tillage Practices: Use tillage practices that reduce crop residue, as the fungus can survive on soybean debris. Deep plowing can help bury infected residue and reduce inoculum levels.

5. Chemical Treatments: While chemical treatments are not the primary method for managing BSR, fungicides can be used as part of an integrated disease management strategy. Here are some examples of fungicides available from FBN that can help manage foliar diseases, which may indirectly reduce BSR severity by improving overall plant health:

   • Priaxor® Xemium® fungicide: Contains fluxapyroxad and pyraclostrobin. It is effective against a broad spectrum of foliar diseases and can help improve plant health.

   • Headline® fungicide: Contains pyraclostrobin and is effective against various foliar diseases. It can be used to maintain plant health and vigor.

6. Scouting and Monitoring: Regularly scout fields for symptoms of BSR, especially during the reproductive stages. Early detection allows for timely management decisions.

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