Causal Agent:
Pythium aphanidermatum
Pythium spp.
Susceptible Turfgrasses:
Affects all turfgrass types
Identification:
Pythium Blight develops quickly under the right conditions and exhibits the following symptoms:
Initial Signs:
Infected areas appear dark gray and water-soaked.
Color Changes:
Spots turn orange or bronze-colored and measure between 0.75 inches (2 cm) to 2 inches (5 cm) in diameter.
Expansion:
Spots may expand to over 6 inches (15 cm), coalesce, and cause rapid blighting of large turf areas.
Characteristic Features:
Presence of grayish fungal mycelium (often described as “smoke rings”).
Leaf Damage:
Leaves become slimy to the touch, collapse, and mat together, leading to plant death.
Favorable Conditions:
Conditions that promote Pythium Blight vary depending on turf type:
Cool-Season Grasses
Weather Conditions:
Hot, humid weather, especially following thunderstorms or heavy rain during summer.
Temperature:
Night temperatures above 68°F (20°C) combined with high humidity.
High-Risk Areas:
Wet, shaded areas and locations with poor surface water drainage.
Vulnerable seedlings are particularly susceptible.
Warm-Season Grasses
Weather Conditions:
Cool, cloudy, and wet periods in fall, winter, and spring.
Common Situations:
Particularly affects ultradwarf bermudagrass putting greens but may also impact other warm-season species.
Management Tips:
Water Management:
Avoid overwatering and improve drainage to minimize standing water.
Irrigation Timing:
Water in the early morning to allow turf to dry out during the day.
Irrigate turf deeply and infrequently early in the day; avoid late-day and night irrigation.
Air Circulation:
Increase airflow in shaded areas by pruning nearby trees or shrubs.
Fertilization:
Maintain balanced nitrogen levels; avoid excessive nitrogen during high-risk periods.
Mowing Practices:
Avoid mowing wet grass to reduce the risk of spreading the pathogen.
