Causal Agent:
Ophiosphaerella korrae
Ophiosphaerella herpotricha
Ophiosphaerella narmari
Susceptible Turfgrasses:
Bermudagrass
Zoysiagrass
Buffalograss
Identification:
Spring Dead Spot (SDS) appears as turfgrass emerges from winter dormancy, presenting the following symptoms:
Patch Appearance:
Bleached, straw-colored circular patches ranging from 6 inches (15 cm) to several feet (up to 1.5 meters) in diameter.
Root Damage:
Affected plants display shortened, dark-brown to black roots, impairing recovery.
Frog-Eye Symptom:
Patches may feature living grass at the center, creating a "frog-eye" appearance.
Distribution:
Patches can occur in isolation or affect widespread areas of turf.
Favorable Conditions:
The following conditions promote Spring Dead Spot development:
Seasonality:
SDS pathogens thrive during cool, wet fall weather when soil temperatures drop below 70°F (21°C), followed by a cold winter.
Winter Impact:
Disease severity increases after mild winters, especially in areas with extended periods of winter dormancy.
Soil and Thatch:
More common in areas with thatch > 0.5 inches (1.3 cm) thick and in exposed, poorly drained locations.
Fertilization:
Heavy nitrogen applications in late summer or fall contribute to disease progression.
Cultivar Susceptibility:
Older bermudagrass cultivars and highly susceptible varieties are at greater risk.
Management Tips:
Thatch Management:
Dethatch regularly to reduce organic material where SDS pathogens thrive.
Proper Fertilization:
Avoid excessive nitrogen applications in late summer or fall to prevent disease escalation.
Soil Health:
Improve soil drainage and aeration to reduce environmental stressors.
Cold-Weather Preparation:
Strengthen turf before dormancy with balanced potassium applications to improve winter hardiness.
Resistant Varieties:
Consider planting SDS-resistant cultivars in areas with a history of the disease.
Potassium
Should also be applied in the fall where the disease is chronic to boost winter hardiness.
Apply Ammonium Sulfate
Or other acidifying nitrogen sources combined with potassium at spring green-up and thereafter until full recovery has been achieved.
Apply Preventive Fungicides
In the fall when soil temperatures are below 70°F. Two applications on a 28-day interval are recommended in most cases.