Common Rust
Symptoms:
- Pustules are oval to circular, and red to dark brown
- Pustules are common on both leaf surfaces
- Rust spores (urediniospores) are cinnamon brown
- Leaves as well as sheaths can be infected, and under severe conditions leaf chlorosis or death may occur
Pathogen Involved:
- Puccinia sorghi (rust fungus)
- Overwinters in the southern U.S. and Mexico (not in the corn belt)
- Urediniospores serve as the repeating stage of this fungus and are blown north to the corn belt in the early summer
Time of Occurrence:
- Occurs in June or July when urediniospores are introduced into the U.S. corn belt via wind
- Pustules are more likely to form after corn silking
Conditions Favoring Disease:
- Cool temperatures (60 - 76°F), heavy dews, and high relative humidity (greater than 95%)
- Approximately, 6 hours of moisture is needed for germination and infection
- Young leaves are most susceptible to infection
Disease Management:
- Use resistant corn hybrids
- Fungicides can be most beneficial if applied early and when are few pustules on the leaves