Net blotch of fescue

The disease is caused by the ascomycete fungus Pyrenophora dictyoides (anamorph Drechslera dictyoides). It is a specialized pathogen that primarily infects species of the Festuca genus. This disease is widely recognized in turf grass management and forage production as a significant factor in plant health decline.

The primary hosts affected by this pathogen include meadow fescue (Festuca pratensis) and tall fescue (Festuca arundinacea). The disease attacks the leaf tissue, leading to chlorosis and necrosis. Heavy infestations can lead to significant biomass reduction, poor turf quality, and stunted growth in both pasture and lawn environments.

Symptoms of the disease initially appear as small brown spots that expand along the leaf veins, creating a distinctive net-like pattern. As the lesion progresses, the tissue turns yellow and eventually dies. Under high humidity, a dark, velvety fungal growth of conidia becomes visible on the leaf surface, which facilitates further spread through wind or water splash.

Optimal conditions for disease development include high humidity, prolonged leaf wetness, and moderate temperatures ranging from 15 °C to 25 °C. The fungus overwinters as mycelium and conidia on infected debris. In the spring, spores are released and dispersed, initiating the primary infection cycle on newly emerging leaves.

Effective management requires an integrated approach to minimize fungal pressure. Cultural practices, such as improving air circulation, avoiding dense canopy moisture, and removing infected clippings, are crucial. Chemical control using fungicides, particularly those containing systemic triazoles or strobilurins, can be applied to suppress disease development in commercial seed crops or intensive turf settings.