Sclerotinia, or white mold, is a fungal disease that cripples sunflower yield potential. Caused by sclerotia, a soil-borne fungal body, it has evolved to become one of the sunflower industry’s most damaging problems.
Factors to Consider
- Disease cycle
- Crop rotation
- Sclerotinia wilt
- Susceptible crops
- Head rot
- Plant canopy
- Middle stalk rot
- Understand sclerotinia attacks. Sclerotinia can harm sunflowers in three ways:
• Roots can grow into a sclerotinia body in the soil, causing wilting and canker formation on the plant’s base. Plant death usually occurs around four to seven days after the first sign of wilting. Wilted plants will not produce harvestable seed. Avoid planting sunflowers into any field where sclerotinia has previously been a problem for broadleaf crops such as dry bean, soybean and canola.
• Head rot causes the head to turn brown and decay, leaving a “straw broom” appearance with the sclerotinia bodies attached to the remains. This reduces seed weight, number of seeds and oil content and is problematic for combining and seed marketability.
• Middle stalk rot due to sclerotinia causes lodging. Serious outbreaks of head rot and middle stalk rot are much more infrequent than wilting.
- Understand disease cycle. Sclerotinia bodies are produced from infection at the base, stem or head of the sunflower. The sclerotinia then fall into the soil and overwinter, causing infection for multiple years. Sunflowers can become infected in two ways. Along with roots coming in contact with a sclerotinia body to cause wilting, plants also can become infected when the sclerotinia bodies produce apothecia, mushroomlike structures that create spores, after seven to 14 days of wet conditions. Wind carries apothecia, causing head rot and middle rot when they land on sunflower heads and stems. Sclerotinia bodies are then produced in the plant, returning to the soil to infect future hosts.
- Manage effectively. There are no chemical controls for sclerotinia. Crop rotation is the best management practice. Planting nonsusceptible crops such as corn, small grains and sorghum in rotation with sunflowers limits sclerotinia bodies in the soil, reducing levels of disease infestation. Lowering crop canopy height also can help. This can be accomplished by reducing plant population and plant size while managing excess nitrogen. Though there are no sclerotinia-resistant sunflower hybrids, North Dakota State University rates varieties each year for sclerotinia vulnerability. Review these by clicking on a hybrid’s product rating to review its level of susceptibility.
Sclerotinia causes problems in many broadleaf crops, including sunflowers. With no treatment options, rotating crops to avoid susceptible fields and limiting canopy size are your top allies. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.
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