TURFGRASS DISEASE IDENTIFICATION (P5)
Causal Agent: Pythium aphanidermatum, other Pythium species
Susceptible Turfgrass: All turfgrass species, especially annual bluegrass, perennial ryegrass, bentgrasses, and tall fescue and bermudagrass
Symptoms: Pythium blight appears suddenly during hot, humid weather. This disease causes greasy, brown circular spots that are initially about 3/4 inch to 2 inches in diameter and then rapidly enlarge in size. The spots are water-soaked and dark-colored early in the morning. They also form fluffy white masses of fungal mycelium (cottony blight) and can coalesce to form large, irregular areas of dead turf. Infected patches may appear bronzish-orange in color.
Conditions Favoring Disease: Pythium blight favors night temperatures of over 68°F. It occurs in areas that experience more than 10 hours a day of foliar wetness for several consecutive days. It is found in the wettest areas of turf and in areas with poor drainage and air circulation. Lush-growing turf growing under nitrogen fertilization is particularly susceptible to the disease.
- Avoid mowing wet turf when the foliar mycelium is evident to minimize spreading the disease.
- Reduce thatch.
- Apply less than 1/2 pound of nitrogen per 1,000 ft2 a month during hot weather.
- Increase air circulation to speed the drying process of the turf.
- Minimize the amount of shade.
- Irrigate turf early in the day. Avoid late-day watering.
- Improve soil drainage.
- Irrigate turf deeply and as infrequently as possible.
- Apply contact and systemic fungicides on a preventive basis.
Occasionally occurs in: CA, CO, IA, IL, KS, ME, MI, MN, MO, MT, ND, NE, NH, NV, NY, OR, SD, UT, VT, WA, WI, WY.
Frequently occurs in: AL, AR, AZ, CT, DE, FL, GA, IN, KY, LA, MA, MD, MS, NC, NM, NJ, OH, OK, PA, RI, SC, TN, TX, VA, WV.
Pythium Root Rot (Root Dysfunction)
Causal Agent: Pythium aphanidermatum, Pythium aristosporum, Pythium graminicola, Pythium vanterpooli, other Pythium species
Susceptible Turfgrass: Species grown on putting greens, such as annual bluegrass, bentgrass, and bermudagrass
Symptoms: Pythium root rot is common on highly maintained turf, such as golf course greens. Although symptoms of Pythium root rot are typically nondistinctive, this disease can appear as yellow, irregularly shaped patches. The affected turfgrass is thin, off-color, and slow growing, while the root system is stunted with reduced volume and vigor. Foliar mycelium does not occur.
Conditions Favoring Disease: Some Pythium species favor temperatures between 32°F and 50°F while others thrive in temperatures between 70°F and 90°F. Pythium root rot occurs in areas with high soil moisture, poor drainage, and low light. It also infects locations with low mowing height and excessive wear.
- Increase the height of cut
- Apply optimum amounts of nitrogen, phosphorous, and potash.
- Reduce mowing frequency and use lightweight mowers.
- Avoid overwatering.
- Apply low amounts of nitrogen in the spring when roots are forming.
- Minimize the amount of shade.
- Improve the drainage of the turf.
- Reduce soil compaction.
- Apply systemic fungicides on a preventive basis.
Occasionally occurs in: CA, CO, IA, ID, IL, KS, ME, MI, MO, MN, MT, ND, NE, NH, NV, NY, OR, SD, UT, VT, WA, WI, WY.
Frequently occurs in: AL, AR, AZ, CT, DE, FL, GA, IN, KY, LA, MA, MD, MS, NC, NJ, NM, OH, OK, PA, RI, SC, TN, TX, VA, WV.