Holcus leaf spot can be found across the United States and Canada. The damage holcus leaf spot does is very minimal, it is a disease that we say is a more cosmetic damage than yield robbing damage. Holcus leaf spot is commonly confused with Eyespot, due to similarities in lesions that the diseases leave on the leaf.
Scouting: Before R1
Before the R1 growth stage is when holcus leaf spot will appear. Lesions start out as a dark green and are oval to irregular shaped and appear to have a water soaked look to them at the margins. The texture of the lesions resemble that of paper. Lesions are typically ¼ inch in diameter and are light brown to a light tan, some may have a light brown border. Holcus leaf spot moves into the plant after a heavy rain and temperatures 77-86 degrees fahrenheit early in the season. The bacteria that causes holcus leaf spot survives in crop residue, and other grass species such as weeds. The infection occurs when the bacteria is splashed onto the leaves or enters through wounds caused by hail, blowing soil particles, and wind.
- Management for Holcus leaf spot rarely occurs.
- There is no in-season treatment
- Fungicides are not warranted for control on holcus leaf spot.