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 causedby 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 arefrequently used interchangeably. It is uncertain at this time whetherthey represent 2 distinct diseases or refer to one common set ofsymptoms. Since signs, symptoms and control procedures are similarfor both diseases, I am considering them a single disease.

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.

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

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 frombentgrass with PythiumRoot Rot/Pythium RootDysfunction

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

Pythium myriotylumstained red in bent-grass root Pythium myriotylum

masserates root tip

Tips of Pythium-infected rootsdisintegrate.

Healthy root tip

Pythium Root Rot/Pythium Root Dysfunction

Management of

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/DysfunctionManagement of

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/DysfunctionManagement of

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.

Pythium Root Rot/DysfunctionManagement of

End of Pythium Root Rot Section