August and September are when you may see certain diseases manifest in your fields. Diseases like sudden death syndrome, brown stem rot and white mold can infect crops earlier in the season but don’t start to show visual symptoms until later in the summer, explains Dean Grossnickle, a Syngenta agronomist for the Slater, IA, Grow More™ Experience site.
With this in mind, now is when you should be on the lookout for Sclerotinia stem rot (white mold) in soybeans. Following a cool, wet spring in 2017, conditions in the Upper Midwest and northern IA fields were right for the germination of sclerotia, allowing for susceptible plants to be infected by the disease. White mold can significantly decrease yield and spread to more fields if not managed properly.
Visual white mold symptoms in soybean fields include a fluffy, white growth and black sclerotia along the stem or bean pods.
To get ahead of the disease, consider the following steps:
- Evaluate your fields for damage: According to Grossnickle, white mold typically causes the tops of soybean plants to start to turn yellow or brown. This is often one of the first visual indicators that the disease is in the field.
- Fungicide use: If you’re using a fungicide, it needs to be timed perfectly to get the desired results, requiring intense scouting and monitoring of the weather. Cultural controls are usually more effective.
- Select varieties that are rated high for white mold resistance: Many NK® Soybean varieties have built-in tolerance to white mold. NK Soybeans S20-J5X brand, S20-T6 brand and S22-J4X brand, which have excellent yield potential and outstanding tolerance to the disease, have had proven performance in areas affected by white mold throughout the Upper Midwest and northern IA. Talk to your local NK retailer if you’d like to add these varieties to your lineup.
- Rotate to a non-host crop: Consider rotating to a non-host crop like corn for a period of time following recent infection in a field. This will help to mitigate the risk of white mold when returning to soybeans down the road
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