Holcus Spot
Symptoms:
- Initial lesions are water-soaked and dark green
- Lesions develop into round or elliptical, tan to white spots that are 2 to 10mm in diameter. Lesions become necrotic with red to brown margins and may develop yellow halos
- Lesions will often form on the tips of lower leaves
- Symptoms can be easily confused with damage from paraquat drift
Pathogen Involved:
- Pseudomonas syringae pv. syringae
- Overwinters in crop debris and will infect through stomata.
- The pathogen has a wide host range including many grasses and dicots
- This pathogen can have ice nucleating activity and may enhance frost injury to corn leaves.
Time of Occurrence:
- Occurs early in the season.
Conditions Favoring Disease:
- Prolonged wet weather
- Warm temperatures (76 to 86°F)
- Wind and early season thunderstorms
Disease Management:
- Crop rotation
- Tillage may be beneficial where appropriate