Soybean crop infected with target spot

Every year, foliar diseases challenge the health and yield potential of soybean crops, and 2021 is no different. As the season progresses, it’s important to stay ahead of common diseases like Septoria brown spot and target spot to help soybeans stay healthy and yield strong at harvest.

If you grow soybeans in the South, you’re probably aware of the damage these diseases can cause. The Crop Protection Network says severe target spot infection on susceptible varieties can lead to significant defoliation, and researchers with University of Kentucky Extension explain that Septoria brown spot can cause yield loss of up to 15%. Additionally, both diseases can overwinter on plant debris, so if you’re planting continuous soybeans this year, keep the potential of increased disease risk top of mind.

Infection from these diseases can lead to lesions on soybean leaves, which can impact the photosynthetic activity needed for soybean plants to reach full yield potential and maximize pod-fill. Here’s what you need to know to catch these diseases early:

Septoria brown spot

• During heavy rains and high wind, spores are carried to the lower canopy of the plant and infect leaf tissue. The disease then spreads upward through the plant under warm, humid conditions.
• Early symptoms of Septoria brown spot appear as light to dark brown spots on the lower leaves. As the infection progresses, spots can turn into irregular shapes and leaf yellowing may occur.

Target spot

• Researchers with North Carolina State University say target spot thrives in very wet conditions when water rests on the plant leaves. Monitor prolonged periods of wet, warm weather, as this can result in a sudden increase in target spot infection.
• Scout the lower leaves early and often for very dark brown, round- to irregular-shaped lesions with concentric rings and yellow halos that resemble targets.

Defending crops against yield-robbing diseases is crucial to helping produce more bushels for every acre. If your area is experiencing favorable conditions for disease development or if your fields have a history of disease, consider a fungicide application at R3-R5 for the most consistent yield protection.

For powerful disease control customized for the tough diseases Southern soybeans face, we recommend Miravis® Top fungicide. Built with 2 modes of action, including Adepidyn® technology, Miravis Top delivers broad-spectrum disease control and dependable plant-health benefits at a lower cost per day, so you get the most value from your investment.¹ Plus, it has reliable activity against strobilurin-resistant pathogens to help you manage disease resistance in your fields.

¹ Cost per day of control is based on product cost per acre and average days of residual control, which may vary by geography and other factors.

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