Summer patch

Summer patch, caused by the fungus Magnaporthiopsis poae, is a severe root-rotting disease that primarily affects high-maintenance turfgrasses. It is particularly notorious for causing significant damage to lawns and sports fields composed of Kentucky bluegrass (Poa pratensis) during the heat of summer.

The pathogen attacks the root system, causing the roots to decay and darken, which prevents the plant from absorbing sufficient water and nutrients. As temperatures rise, the compromised root systems cannot support the plant, resulting in rapid wilting and eventual death of the affected turf patches.

The symptoms of Summer patch typically appear as circular, crescent-shaped, or irregular patches of necrotic turf. Often, the grass within these patches turns a dull, reddish-brown color before turning straw-colored. A unique feature of this disease is the "frog-eye" symptom, where some green, healthy-looking grass may survive in the center of the patch.

Disease development is heavily favored by prolonged periods of high soil temperatures (above 20°C/68°F) and excessive soil moisture. Factors such as compacted soil, high pH levels, and a heavy thatch layer provide an ideal environment for the fungus to thrive and infect susceptible turfgrass species.

Integrated management is essential for controlling the disease. Key strategies include practicing proper irrigation techniques to avoid over-saturation, alleviating soil compaction through regular core aeration, and managing soil pH to maintain a slightly acidic environment. Additionally, applying preventative systemic fungicides early in the season, when soil temperatures reach the threshold, is highly effective in mitigating the impact of the infection.