Causal Agent:
Colletotrichum cereale
Susceptible Turfgrasses:
Creeping bentgrass
Annual bluegrass
Identification:
Anthracnose can appear as either foliar blight or basal stem rot. Key identifying characteristics include:
Bright yellow leaves and thinning turf.
The presence of distinctive black fruiting bodies (acervuli) with black hairs on infected leaves and stems.
On putting greens, symptoms often begin as small yellow speckles or spots. These can quickly lead to irregularly shaped areas of plant death.
Upon close inspection, look for blackened stem bases and acervuli, particularly on bentgrass.
Favorable Conditions:
Anthracnose is influenced by both cool, wet weather and subsequent heat stress. It typically thrives under the following conditions:
Root Infection Periods:
Occurs in spring or fall during cool, wet weather.
Exacerbating Factors:
Symptoms worsen during heat stress when soils dry out rapidly.
Commonly seen in turf with a root zone soil pH above 6.5.
Risk Factors:
New Sand-Based Constructions: Particularly vulnerable due to soil composition.
Cleared Woodlands: Recently established turf in these areas is more susceptible.
Persistent Issues:
Typically emerges in the second year after establishment.
Severity usually decreases over a 2 to 5-year period as bentgrass matures.
In rare cases, it can remain a chronic issue, especially with excessive rainfall in late winter and spring on older sites.
Prevention Tips:
Soil pH Management: Maintain a balanced soil pH below 6.5 to reduce susceptibility.
Water Management: Ensure consistent moisture levels to avoid rapid soil drying.
Nutrient Management: Apply balanced fertilizers to avoid plant stress.
Aeration: Improve air circulation and reduce soil compaction to support healthy root growth.
Management Tips:
Increase height of cut and use solid rollers in summer.
Apply small amounts of nitrogen (~ 0.1 to 0.2 lb N/1,000 ft2) periodically throughout the growing season.
Divert traffic and minimize mower stress.
Light and frequent sand topdressings throughout the growing season help suppress the disease by cushioning stem bases.
Avoid drought stress; syringe and hand water when necessary.
Minimize encroachment and domination of annual bluegrass using appropriate growth regulators and/or herbicides.
Preventive applications of appropriate systemic fungicides are highly effective, especially when combined with small amounts of nitrogen and an increase in mowing height.
Curatively, apply an appropriate contact fungicide and systemic fungicide in combination with a small amount of nitrogen.
Frequently occurs in:
In all regions where annual bluegrass can dominate golf greens. Less common and more easily controlled in bentgrass if quickly diagnosed.
