Early infection of susceptible varieties can cause serious reduction in seed yield and oil content.
Later infections cause less damage.
Late planted fields of susceptible hybrids are generally more severely damaged by rust than earlier planted fields. Tips Figure 2. Host Crops Sunflower, wild sunflower Biology Sunflower rust spores overwinter on the debris from infected sunflower leaves and stems. In the spring, the spores germinate to infect volunteer seedlings, wild sunflowers or new young plants in nearby fields. Spore production and infection continue to occur.