Physoderma Brown Spot
Symptoms:
- Initial lesions are tiny, round, and yellow spots
- Later, lesions turn to a brown or reddish color and merge together to form irregular blotches
- Lesions often occur in bands on leaves as well as on sheaths and stalks, but rarely occur on ear husks and tassels
Pathogen Involved:
- Physoderma maydis (a fungus)
- Overwinters in infested tissue or soil
- Primarily occurs in regions with high temperatures and much rainfall
- This disease is not considered to be important in the United States, however, when conditions are favorable, severe damage can occur
Time of Occurrence:
- Corn plants are most susceptible 50 to 60 days after germination
- This disease will occur most often after late whorl
Conditions Favoring Disease:
- Infection usually occurs on leaf tissue within the whorl, where water has gathered
- High temperatures (72 - 86°F) and heavy rainfall
Disease Management:
- Infection may be reduced by tillage or destroying crop residue
- Resistant corn hybrids may be available