Pythium root rot

Pythium volutum is a destructive oomycete pathogen responsible for a severe form of root rot that primarily affects managed turfgrasses. This disease compromises the integrity of the root system, leading to widespread thinning and potential death of the grass stand, which creates significant management challenges for golf courses and turf professionals.

The pathogen specifically attacks the roots of cool-season grasses, most notably Agrostis (bentgrass) and Poa annua (annual bluegrass). By invading the cortical cells of the roots, P. volutum disrupts the plant's ability to uptake water and essential minerals, eventually leading to systemic decline of the turf.

Symptoms often appear as irregular, yellowing, or orange-brown patches throughout the turfgrass area. Unlike foliar blight, the symptoms of P. volutum root rot are often subtle at first, with affected plants showing signs of drought stress despite adequate irrigation. Closer examination of the roots reveals a brown, necrotic, and disintegrated root system.

Development and dissemination of this pathogen are heavily influenced by environmental conditions, particularly high soil temperatures and saturated soil moisture. These conditions facilitate the release and movement of zoospores through the soil profile and irrigation systems, enabling the disease to spread rapidly across large areas of a playing surface.

Effective management requires an integrated approach. Cultural practices such as core aeration, adjusting irrigation intervals to promote soil drying, and balanced nitrogen fertilization are critical for minimizing risk. When environmental conditions remain conducive to disease pressure, the strategic application of specific systemic fungicides remains the primary chemical control method to prevent substantial damage.