Arrhenia spathulata

Arrhenia spathulata is a basidiomycete fungus known to cause significant degradation of turfgrass areas. Often classified under the category of lawn-damaging fungi, it primarily affects the density and health of ornamental lawns, acting as a pathogen that thrives in moist and poorly ventilated environments.

The primary hosts for this fungus include common lawn grasses such as Kentucky bluegrass (Poa pratensis) and various species of fescue. The pathogen colonizes the thatch layer and the base of the grass blades, where it interferes with the plant’s nutrient uptake. This interaction causes yellowing, wilting, and eventually the death of grass patches.

The symptoms of an Arrhenia spathulata infestation are identifiable through the presence of small, spatulate-shaped fruiting bodies emerging from the soil. Surrounding these fruiting bodies, the lawn usually displays irregular, thinned-out areas that gradually transition from a pale green to a necrotic brown color. If left untreated, these patches can expand, creating unsightly gaps in the turf.

Development and spread are facilitated by excessive moisture, high humidity, and poor soil drainage. The presence of thick thatch, restricted air circulation, and long periods of standing water creates an optimal habitat for the mycelium to proliferate. The disease is most aggressive during cool, wet seasons, which are characteristic of its opportunistic lifecycle.

To effectively manage and control this pathogen, a robust cultural management program is essential. Key strategies include verticutting to reduce thatch buildup, mechanical aeration to improve soil aeration and drainage, and the implementation of a precise irrigation schedule to prevent surface water accumulation. In severe cases, the application of targeted fungicides may be necessary to suppress the fungal growth and allow the grass to recover.