Sunflower Rust

P. helianthi produces five distinct spore stages during its life cycle. The uredinial stage is the repeating stage consisting of uredinia as red-brown, cinnamon-colored pustules containing thousands of urediniospores. During fall, these pustules turn black and begin producing overwintering teliospores in the telial stage. In early spring, the teliospores germinate to produce basidiospores, which disperse to infect sunflower seedlings. These infections elicit the pycnial and aecial spore stages, where flask-shaped pycnia is found embedded in the upper surfaces of leaf tissues, and aecia is seen directly below the pycnia on the dorsal side of leaves. Aeciospores that develop in the aecia reinfect sunflowers and reset the cycle by creating new uredinia.