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. A soilborne pathogen that travels via water with “swimming” spores, downy mildew can be costly for growers. However, by monitoring and proactively implementing the right cultural and chemical management practices, growers can manage the disease and preserve yield.

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 and systemically invade the rest of the plant, causing severe stunting and often killing plants. 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 stay in soils for up to a decade. If infected plants are able to survive, they develop thick, yellow leaves and a white cotton-like substance appears on the underside of the leaves.

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 is offering Bion seed treatment plant defense activator in 2015 as a component of CruiserMaxx Sunflower seed treatment, combination of separately registered products. CruiserMaxx Sunflower plus Bion seed treatment insecticide/fungicide provides superior insect and disease protection, increased germination and emergence, improved stand establishment and enhanced downy mildew protection.

Nathan Popiel, Syngenta agronomy service representative, stresses that fungicides are key when it comes to downy mildew prevention, “We want to use as many precautions as we can. It is extremely important to plant a downy mildew tolerant hybrid and treat it with a product, like Bion, to give it added protection. The great aspect of Bion is, when combined with Dynasty® fungicide, it enhances downy mildew protection, leading to healthier plant establishment.”

In addition to choosing the best-suited variety, be sure you are using the best protection methods for your field. It’s also important to speak with your local seed agents and agronomists who can provide recommendations about crop management. In doing so, you’ll help ensure your sunflower crop gets off to a healthy start and remains competitive throughout the season.