Anthracnose Foliar Blight and Basal Rot

Symptoms and signs

Anthracnose foliar blight appears as irregular yellow or bronze patches of diseased turf. Symptoms on individual plants first appear as yellow or red lesions on the oldest (outermost) leaves, then progress to a blighting of younger leaves and shoots. Occasionally, fungal fruiting structures called acervuli can be observed with a good quality hand lens on diseased leaves and stems. Acervuli resemble small, black pin cushions and are the location of spore production.

Anthracnose basal rot symptoms vary depending on the grass species affected. On annual bluegrass, symptoms appear as a bright yellowing of the turf in irregular patches. Affected bentgrass turf typically appears as irregular red or bronze patches are rarely appears yellow. On individual plants affected with anthracnose basal rot, a dark brown or black color is present at the base of the plant. As the disease worsens, the darkening (rotting) progresses up the stem and acervuli can be observed with a hand lens on stem and leaf tissue.

Disease Cycle

The causal fungus, Colletotrichum graminicola, survives the winter as dormant resting structures called sclerotia and as dormant mycelium in infected plant debris. During early spring outbreaks of anthracnose basal rot, the fungus, which may have overwintered in the plant, initiates infection at the base of the plant. Outbreaks of anthracnose foliar blight and / or basal rot can result when spores produced in acervuli are dispersed by splashing water or tracked by mowing equipment from one area to another. These spores then germinate and cause new infections on other plants. Anthracnose is likely to occur when plants are growing slowly (during periods of hot and cold temperatures), during overcast periods, and in high humidity conditions.

Cultural Control

Proper fetilization and maintaining good soil physical conditions are the most effective approaches to managing anthracnose. If your turf is underfertilized, increase the rate and / or frequency of nitrogen fertilizer applications. This will improve resistance to the disease and sid in turf recovery. Add potassium and phosphorus if your soil test report indicates a need. Improved drainage and a regular aeration program will reduce excess soil moisture, alleviate compaction, and improve root growth, creating conditions that are less favorable for anthracnose.

Chemical Control

Fungicides are only used to control anthracnose on golf courses. Preventative (before the disease occurs) applications of fungicides are generally more effective in controlling anthracnose foliar blight and basal rot than curative (after the disease appears) applications. Application timing will vary from one region to another and possibly from year to year at the same location. The best way to time your applications is to keep records for several seasons of the environmental conditions under which the disease occurred on your course, then apply fungicides when conditions are conducive for disease development.