Common Rust (fungus - Puccinia sorghi): The fungus erupts from the leaf tissue in round to oval areas called pustules, with cinnamon brown spores . These spores eventually turn black. Rust is favored by cool temperatures and high humidity. Older tissue is generally resistant. There are numerous physiologic races of this fungus. Control disease with slow rusting resistant hybrids (photo). Fungicides are usually not economically practical. High summer temperatures usually reduce the disease.
