Tech Notes Issue 1

It seems like it  never gets too hot for Pythium blight

Pythium blight is a severe disease of many turfgrasses during the summer months. Cool season turfgrasses like creeping bentgrass are most susceptible but couchgrass and other warm season turfgrasses can also be infected under the proper environmental conditions.

Pythium attacks when daytime temperatures are above 30 C and nighttime temperatures remain above 20 C. Wet humid conditions along with high temperatures are most favorable for this disease. Pythium is most severe on turf that is poorly drained or have little air movement (shaded conditions).

Extreme Heat Stress Can Result in Curvularia Diseases

With the high summertime temperatures turfgrass plants become susceptible to diseases not normally considered a problem. Curvularia species (ex. C.  lunata , C. trifolii, C. eragrostidis) are normally weak pathogens but can become severe on turfgrass plants weakened from heat and/or moisture stress.

Curvularia disease symptoms are most evident on senescing plant tissue primarily leaves. On senescing tissue conidia from the pathogen infect and sporulate profusely. Symptoms initially appear as indistinct yellow and green mosaic type of pattern extending from the leave tip down (the oldest part of the leaf is the tip).

The leaves eventually shrivel and turn a grayish color; except with creeping bentgrass where the leaves appear tan. If warm wet weather occurs rapid infection of plant tissue can occur.

Curvularia is a difficult disease to control because the turf plants are under severe environmental stress. Practices like minimizing soil compaction, providing a better growing environmental condition, and proper cultural management (balanced fertility, proper watering, etc.) can help make for a healthier turfgrass plant.

In some instance registered fungicide applications would be warranted.

 Picture: Advanced stage of Curvularia with the turf showing the grayish color. Curvularia can live saphrophytically on plant debris