You Are Here: Management Updates 2003 Archive October 2, 2003

Date: October 2, 2003
Category: Diseases
Subject: Gray Leaf Spot Alert

Gray leaf spot, caused by Pyricularia grisea, is a potentially devastating disease of perennial ryegrass. It has just been confirmed in a sample of a golf course fairway from eastern MA. It is difficult to predict if the upcoming cold nights will stop the fungus although it should certainly slow it down. The other good news is that this is a leaf spot disease, so foliar applications of several fungicides will be effective if caught at the early stages: Heritage™, Compass™, thiophanate-methyl (e.g. Cleary's 3336™). DMI fungicides (Eagle™ or Banner™) and chlorothalonil also work but are not as effective. A single application of one fungicide in the first group should get you through the end of the season for this year. The disease is most common in perennial ryegrass golf roughs, fairways, and tees. Turf managers of grounds, lawns, and athletic fields composed of perennial ryegrass should also be on the lookout for unusually severe leaf spot activity. Seedlings are most susceptible. Other leaf spots of perennial ryegrass can look identical in the early stages. The disease can progress so quickly that it may appear to be drought stress. The disease does not attack other turfgrass species (bluegrasses, bentgrasses, fescues)- another diagnostic clue. Submit a sample to the UMass Turf Disease Diagnostic Lab if you are uncertain. Once you have had the disease, you will want to be on guard for it in the future.

- Submitted by: Dr. Gail Schumann