Blog Post

Don’t let downy mildew knock down sunflowers

With the ability to wipe out large portions of sunflowers and significantly decrease yield, downy mildew is one of the most devastating diseases that can strike sunflower fields. However, by monitoring and proactively implementing the right cultural and chemical management practices, growers can preserve yields.

Favoring cool, wet conditions, downy mildew is most prevalent in low-lying areas of sunflower fields with poor drainage, where water can pool and downy mildew spores can freely travel and infect large groups of plants. The disease spores enter the roots of sunflower plant and systemically invade it, causing severe stunting and often killing the plant. Downy mildew can occur in all sunflower-producing regions of the U.S. and is most common early in the season, right after planting.

Symptoms and management:

Downy mildew stays with its sunflower host until it reaches maturity, at which point it forms an overwintering structure that allows the pathogen to survive in soil for up to a decade. If infected plants are able to remain alive, they develop thick, yellow leaves and a white cotton-like substance appears on the underside of the leaves.

infected leaf

Despite the potentially devastating effects of downy mildew, there are management options for controlling the disease before it can impact yields:

  • Monitor fields
  • Control wild and volunteer sunflower
  • Observe environmental conditions (cool temperatures, prolonged rainfall)
  • Plant downy mildew tolerant sunflower hybrids
  • Use a seed treatment that protects against downy mildew

Besides planting tolerant hybrids, growers can proactively protect against downy mildew by using seed treatments. A fungicide seed treatment is the only effective crop protection product for downy mildew control, providing additional protection for less tolerant hybrids and areas most at-risk for the disease.

Because downy mildew is known to evolve and adapt quickly, Syngenta offers CruiserMaxx® Sunflower plus Bion® seed treatment insecticide/fungicide for excellent insect and disease protection, increased germination and emergence, improved stand establishment and enhanced downy mildew protection.

In addition to choosing the best-suited variety and seed treatment, be sure you are using the best protection methods for your field. In doing so, you’ll help ensure your sunflower crop gets off to a healthy start and remains competitive throughout the season.

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