The Ohio State University

Home TurfNotes In the last two weeks samples have been received of creeping bentgrass (in several cases 'L-93') putting green samples where Leaf Spot is present and causing considerable damage. Due to the cool temperatures it appears that this is not red leaf spot (pathogen: Drechslera erythrospila) but a Bipolaris spp. or Drechslera spp. leaf spot. As cultures are completed and the pathogen is identified additional information will be posted. In one case this is the second year in a row that the disease has developed and caused significant damage.

The symptoms of this disease are similar to that of anthracnose and Microdochium patch (Pink Snow Mold) however the color and environmental factor may not fit well with these diseases. A key diagnostic aid is that the creeping bentgrass is affected and not the Poa annua. Leaf lesions appear a tan to reddish brown color, but are difficult to observe on low cut greens, the leaf lesions may be seen on the higher cut collars and surrounds. At times the tan colored center may be small or not present. Under severe outbreaks the leaves will wither, or dieback and the turf stand will thin, and collapse under server out breaks of the disease.

Historically the best fungicides to consider are iprodione and vinclozolin. Remember that iprodione and vinclozolin are local penetrants and will have to be reapplied at a more frequent interval than systemics since they are removed by mowing. If the disease is active use high label rates. In general the sterol inhibitors are not highly effective especially if the disease has progressed and in an advanced stage. If there is a history of the problem start making applications in spring early before symptoms development.

Posted by Joseph Rimelspach