TechNotes July 29 – Pythium Blight, Soil Temps

PYTHIUM BLIGHT WILL PROBABLY RETURN. With the cold front that has pushed through the northern and upper Midwest, conditions favorable for pythium blight have dropped. However, Pythium blight remnants are present and will resume with the arrival of favorable conditions.

Pythium blight remains a serious problem during hot humid weather on creeping bentgrass and perennial ryegrass turfs. This disease can also attack bermudagrass under hot wet conditions. Generally, this disease is most severe on turf sites that are wet or poorly drained. This disease often appears first in areas where water drains. Pythium blight on creeping bentgrass may initially appear first in stressed areas. These areas include high traffic areas where compaction occurs like the ends of fairways where mowers may turn. On tees, pythium may initially appear around divots where the turf is under additional stress. On perennial ryegrass pythium blight is often confused with browh patch. Although brown patch is easily diagnosed on creeping bentgrass, on perennial ryegrass it often appears similar to pythium blight.

Pythium blight is most apparent when temperatures occur between 85 and 95 F (30 to 35 C) and nighttime temperatures remain above 70F. However under extremely humid and wet conditions pythium will occur at nighttime temperatures below 70 F, which was the case in the Chicago area two weeks ago. There are numerous species of pythium that can potentially infect turfgrasses. In the southeastern United States a malady of creeping bentgrass that causes its decline has been associated with a pythium species. Generally speaking control is most effective when applied preventatively.

SOIL TEMPERATURES.