Holcus leaf spot of corn
Holcus leaf spot is caused by the bacteria Pseudomonas syringae pv. syringae. Holcus leaf spot usually does not cause major losses. Leaf spots are initially oval to irregular, dark green, water-soaked at the margins, and may have a light brown border. Later, lesions dry out and turn light tan, usually without a border. The dry lesions have a papery texture.
Holcus leaf spot often follows warm (77-86°F), rainy weather early in the season. Holcus leaf spot lesions with water soaked edges. Image: D. Mueller
Holcus leaf spot lesions may have a light brown border. Image: A. Robertson
Most hybrids have adequate resistance. Other management practices are rarely warranted and fungicides are not effective against this bacterial disease.