Background:
Common rust is created from the fungus Puccinia sorghi and occurs in every growing season. Rust pustules begin to appear in late June. It appears as chlorotic flecks on the leaf surface before turning into powdery, brick-red pustules as the spores break through the leaf surfaces. The pustules are ⅛-inch-long ovals that are either scattered sparsely or in clusters. As the pustules age, the spores will turn black and continue to erupt through the leaf surface. When these spores erupt, the rust can spread to the husks, leaf sheaths and stalks.
Scouting:
When scouting, observe the leaves for little red speckles along with a yellow leaf. Also be on the lookout for lesions across the leaf.
Life Cycle:
The fungus overwinters in subtropical and tropical regions in Central America. Wind carries its spores to the Midwest region of North America. The rust will develop in high humidity with night temperatures between 65°F -70°F and moderate daytime temperatures. (Crop Protection Network Common Rust)
Management:
- Plant non-susceptible hybrids.
- Use fungicides as early as possible. (University of Minnesota Common Rust)
