Pythium Root Rot/Pythium Root Dysfunction caused by Pythium graminicola, P. torulosum, P. vanterpoolii, P. myriotylum, P. ultimum, P. irregulari, P. rostratum, P. volutum and Several other species

Previously, we covered Pythium Blight, a foliar disease caused by Pythium aphanidermatum and P. ultimum. In this section, we will review Pythium Root Rot/Pythium Dysfunction which is caused by several other species of Pythium. The disease names Pythium Root Rot and Pythium Dysfunction are frequently used interchangeably. It is uncertain at this time whether they represent 2 distinct diseases or refer to one common set of symptoms. Since signs, symptoms and control procedures are similar for both diseases, I am considering them a single disease.

All turfgrass species are susceptible. Pythium Root Rot/Pythium Root Dysfunction Susceptible Grasses All turfgrass species are susceptible. Cool season grasses are more susceptible than warm season grasses. Creeping bentgrass, perennial ryegrass, and tall fescue are most susceptible.

Favorable Environment - High root zone water content Pythium Root Rot/Pythium Root Dysfunction Favorable Environment - High root zone water content low oxygen in root zone Wide range of temps – Depends on which Pythium species is causing disease.

Pythium Root Rot/Pythium Root Dysfunction on creeping bentgrass. Note irregular straw-colored patches. Only foliar symptom is die-back from tip of leaf downward.

Leaf tip die-back from bentgrass with Pythium Root Rot/Pythium Root Dysfunction

Pythium Root Rot/ Pythium Root Dysfunction thinning, stunting and yellowing of turf irregular pattern die-back of leaves from tip down

Pythium Root Rot/Dysfunction (left) Note stunting of roots.

Pythium Root Rot/Dysfunction causes roots to be stunted but not discolored like Take-All Patch.

Pythium myriotylum masserates root tip Pythium myriotylum stained red in bent- grass root Pythium myriotylum masserates root tip

Healthy root tip Tips of Pythium- infected roots disintegrate.

Management of Pythium Root Rot/ Pythium Root Dysfunction

Pythium Root Rot/Dysfunction Management of Pythium Root Rot/Dysfunction Resistant Species and Cultivars In southeast U.S., creeping bentgrass is most susceptible turfgrass. High temperature-tolerant cultivars of bentgrass e.g. Crenshaw, L93, A-1, A-4, G-2 may be less susceptible than other cultivars.

Pythium Root Rot/Dysfunction Cultural Control Management of Pythium Root Rot/Dysfunction Cultural Control - Avoid high N applications in spring. Maintain moderate to high levels of P and K according soil test. Improve surface and subsurface drainage. Core aerify every 3-4 wks. to enhance oxygen movement into root zone. - Control nematodes. Decrease shade and increase air circulation.

Pythium Root Rot/Dysfunction Chemical Control Management of Pythium Root Rot/Dysfunction Chemical Control Contract fungicides – ethazole, cyanofamid – 7 to 10 days control Localized penetrant – pyraclostrobin – 10 to 14 days control. - Preventive treatments are better than curative.

End of Pythium Root Rot Section