Anthracnose diseases are common in golf course putting greens established with Creeping Bentgrass or Annual Bluegrass. Anthracnose may develop as a foliar blight, in which the turfgrass leaves are infected, or a basal rot, which attacks the leaf sheaths, crowns, and stolons of the plant.
Anthracnose symptoms are highly variable, appearing yellow to orange in color and in an irregular pattern, in small freckle-like spots, or in circular patches up to 1’ in diameter. Symptoms are typically most severe in areas that are stressed from low mowing, excessive traffic, or inadequate irrigation or fertilization.
On individual plants, symptoms first appear on the oldest leaves, which die back from the tip, and gradually progress to the younger leaves.
Symptoms of anthracnose foliar blight will initially be limited to the leaves, leaving the crowns, leaf sheaths and stolons healthy. In the case of basal rot, the leaf sheaths, crowns, and stolons will be dark and rotten. The anthracnose pathogen produces spores inside of structures called acervuli, which are black, saucer-shaped pads with black spines (setae) protruding from them. These can be seen on the infected leaves (foliar blight) or basal tissues (basal rot) with a magnifying glass or small microscope.
In creeping bentgrass putting greens, anthracnose basal rot is most active during hot weather in the summer, whereas the foliar blight is most common during cool and cloudy conditions. The opposite is true on annual bluegrass, with the basal rot being most severe in cool, cloudy weather and the foliar blight more common during hot, dry weather.