3 Sunflower Diseases That Can Cause Significant Damage

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There are 3 primary diseases that sunflower growers should be aware of because they can regularly cause enough damage to post significant financial concerns for growers. These diseases are white mold, downy mildew and rust.

White Mold

White mold can enter the plant in 3 ways: the flowers at the head of the plant, dead tissue or lesions on the stalk or from the roots. The ability to spread through roots makes uninfected plants near infected ones prime targets.

Wet soil conditions are ideal for white mold. Sclerotia bodies can survive a long time in the soil. Prevention methods include crop rotation. Growers should look to plant in a field that doesn't have a history of white mold or hasn't had a broadleaf crop in it for three to four years.

Downy Mildew

Like white mold, downy mildew has become a common fungus among sunflowers in recent years. The disease stunts plant growth early, limiting seed production. It commonly appears in places featuring cool, water-saturated soils and areas that drain slowly.

There are many races of the disease. The ones a grower will see in his or her fields depend on location. For example, in eastern North Dakota, there are 4 predominant Races. Pioneer’s newest advanced hybrids offer tolerance to those races


Rust can have significant economic impacts in any sunflower region. In the Dakotas and parts of Minnesota, yields have been cut from 2,000 pounds to 500 pounds per acre.

The pathogen that causes rust overwinters on plant debris from previous years. Because the disease goes through its life cycle during the season, infection can increase as the growing season goes on. Favorable weather conditions such as a warm and moist environment can accelerate rust development as well. The rust pustules are cinnamon red and easily recognizable.

Out of all the sunflower diseases, this is probably the most treatable. There are a number of fungicides growers can use for control. Treating after the R6 stage tends to be less economically effective.

Treatment & Prevention

A single fungicide application often will be ineffective for preventing sunflower diseases. High-end producers are using fungicide applications at different stages of sunflower life. Some growers are treating once at the mid-to-late vegetative stage and again at the early reproductive stage. These applications often are paired with an insecticide application. Producers also see success when alternating modes of action in their treatments.