Causal Agent:
Magnaporthiopsis poae
Susceptible Turfgrasses:
Annual bluegrass
Creeping red fescue
Kentucky bluegrass
Creeping bentgrass
Identification:
Summer Patch symptoms develop as follows:
Early Stages:
In Kentucky bluegrass, turf appears slow-growing, thinned, or wilted with bleached-white leaf tips, resembling dollar spot.
Patch Formation:
Circular or irregular patches ranging from several inches (approximately 5 cm) to 18 inches (45 cm) in diameter develop.
Active patches display a bronze-colored periphery, eventually turning straw or tan-colored.
Specific Signs:
In annual bluegrass on greens, symptoms appear as yellow rings or spots.
In creeping bentgrass mixtures, infected areas may turn reddish-brown or bronze.
Favorable Conditions:
Summer Patch thrives under the following conditions:
Root Infection:
Begins when soil temperatures exceed 65°F (18°C).
Symptom Development:
Foliar symptoms are favored when:
Day temperatures exceed 85°F (29°C).
Night temperatures remain above 70°F (21°C).
Affected Sites:
Most common during summer heat in sunny areas.
Reduced occurrence in shaded locations.
Particularly vulnerable sites include:
Slopes and low areas prone to flooding.
Compacted soils with pH above 6.8.
In greens, it thrives in sunny, wet conditions, especially near surface water drainage patterns.
Management Tips:
Soil Monitoring:
Utilize soil sensors to track soil temperature and moisture, allowing for early intervention.
Fertility Management:
Maintain balanced fertilization to avoid excess nitrogen, which can increase disease susceptibility.
Irrigation Practices:
Avoid overwatering, especially in compacted or low-lying areas. Water deeply but infrequently.
Aeration and Drainage:
Aerate to reduce soil compaction and improve drainage.
pH Management:
Maintain soil pH between 6.0 and 6.5 to limit pathogen activity.
Chemical Control:
Apply fungicides targeting Magnaporthiopsis poae during root infection periods for effective control.
Preventively apply on a 21-28 day interval beginning in late-spring (i.e., mid-May most regions) until early August. Do not expect 100% disease control. Where chronic, use lower labeled rates on 14-day intervals. Application timing coincides with 65°F soils temperatures for three consecutive days at a 2" depth.
