Anthracnose is caused by Colletotrichum graminicola, a fungus that survives and thrives on dead and decaying organic matter. Although anthracnose may occur occasionally in turf maintained for athletic fields, professional landscapes, and residential lawns, it is primarily a disease of intensively managed annual bluegrass and creeping bentgrass used on golf courses. The anthracnose pathogen can cause two kinds of infections: a foliar blight (during stressful summer conditions), or a basal stem rot in annual bluegrass and creeping bentgrass (during cool, wet periods in spring). It is not clear how the foliar blight and basal stem rot diseases are related. The basal rot anthracnose is the more destructive phase of the disease.Foliar Blight AnthracnoseA variety of summer stresses, including heat, drought, nitrogen deficiency, close mowing, and compaction, predisposes turfgrass to the foliar blight phase of anthracnose. Stress leads to premature decline and senescence, and limits the potential for turf recovery.
There also is evidence that pre-emergence herbicides also stress plants, predisposing them to anthracnose infection.The anthracnose fungus readily colonizes dead leaf blades under stressful conditions. When conditions are especially favorable, green leaf tissues and possibly crown tissues are infected, resulting in serious damage to the turf stand. Foliar blight anthracnose spreads largely by rain-splashed spores. Infection does not result in any visible surface mycelium.From a distance, anthracnose-infected turf tends to have a yellow-orange cast and appears to lack its usual vigor. Affected areas are not well-defined, although they may occur in clusters. Irregularly shaped tan leaf spots may occur on infected leaves. Anthracnose leaf spots appearing on green leaf tissues indicate aggressive disease activity. Typically, infected leaves turn yellow and decay from the tips downward. Foliar blight usually follows normal summer senescence of annual bluegrass.
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