Anthracnose

Colletotrichum cereale

Cool-Season Grasses Highly Destructive Fungus

Symptoms

Two phases: foliar blight (yellowing leaf blades with black acervuli visible under magnification) and basal rot (crown and stem rot causing plant death). Most destructive on annual bluegrass putting greens.

Foliar phase: yellow to reddish-brown leaf blades with irregular patches on putting greens
Basal rot phase: blackening of crown and lower stem tissue — plants pull out easily
Tiny black fruiting bodies (acervuli) with dark setae visible on infected tissue with a hand lens
Patches range from a few inches to several feet; often diffuse and irregular
Basal rot phase is most lethal and most difficult to recover from

Signs

Black acervuli (spore-producing structures) with dark bristle-like setae visible on infected crown and leaf tissue with a 10–20x hand lens — a definitive diagnostic feature
Salmon-colored spore masses (conidia) may ooze from acervuli under moist conditions
Dark discoloration of crown and basal stem tissue visible when plants are pulled and split longitudinally

Biology

C. cereale persists in infected plant debris and thatch. Conidia are spread by water and mowing equipment. The pathogen is an opportunistic pathogen of physiologically stressed turf — heat, drought, compaction, and low mowing all increase susceptibility. Basal rot phase occurs under cooler conditions than foliar blight.

Favorable Conditions

Temperature range: 78–95°F foliar; 60–70°F for basal rot

Prolonged heat and humidity stress on annual bluegrass
Low mowing heights, especially below ¼ inch
Low nitrogen or imbalanced nutrition
Compacted soils with poor rooting
Heavy traffic and mechanical stress
Drought stress or waterlogged soils

Cultural Practices

Raise mowing height even slightly — significant impact on disease severity
Maintain adequate nitrogen — light, frequent applications in summer
Reduce compaction through core aeration and deep tine cultivation
Manage traffic to reduce mechanical stress during high-risk periods
Ensure adequate potassium for plant stress tolerance
Use growth regulators judiciously — excessive suppression increases stress
Topdressing with sand improves drainage and reduces organic matter accumulation

Related Reports

No published reports yet for this disease.

Reports will appear here as they are peer-reviewed and published.