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Stay Alert for These Common Soybean Diseases in 2021

March 17, 2021
this agronomic image shows frogeye leaf spot

Soybean leaf infected with frogeye leaf spot.

Spring has sprung and the weather is warming up. It’s now important to prepare for yield-reducing foliar diseases that thrive in warm, moist weather. 2 diseases that should be on your radar this season are brown spot and frogeye leaf spot (FELS).

If you grow soybeans in the Midwest, you’re no stranger to brown spot. Researchers with the University of Nebraska-Lincoln estimate this common disease can cause yield losses from 8-15%. Other adverse effects of brown spot include leaves prematurely dropping and significant defoliation.

Another major threat to soybeans is FELS, which can cause up to 30% yield loss, and the spread of strobilurin-resistant FELS has continued in the Midwest. In 2019, 73 cases of the disease were recorded in IA and 10 in NE.

Both brown spot and FELS are difficult to manage past a specific growth stage, so assess the potential for high disease pressure early and consider these proactive strategies to protect your bottom line:

  1. Evaluate your crop rotation history. Fields growing continuous soybeans are more vulnerable to brown spot and FELS because the pathogens causing these diseases can overwinter on soybean residue and appear the next season. Take preventive measures by practicing crop rotation and tillage.
  2. Know the symptoms. Scout early and often. While you scout your fields, you may find it challenging to distinguish brown spot from FELS. Early symptoms of brown spot appear as light to dark brown, irregular spots on the lower and upper leaves. FELS is identified by small, dark lesions that later expand and develop a purple border.
  3. Apply a fungicide on time. Planting a susceptible soybean variety in fields with short rotations between soybean crops or a history of these diseases may warrant a preventive fungicide application. To protect soybeans against brown spot, apply a fungicide between the R3-R6 growth stages. Optimal application timing to manage FELS is between the R3-R4 growth stages.

Protect your soybeans with Miravis® Neo fungicide to prevent yield loss from key diseases like brown spot, FELS and more. Containing three active ingredients – including Adepidyn® technology – Miravis Neo offers broader, longer-lasting disease control and unmistakable plant-health benefits to help deliver more bushels more often.

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