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.