TURFGRASS DISEASE IDENTIFICATION (P13)
Other Fungal Diseases
Red Thread and Pink Patch
Causal Agent: Red thread—Laetisaria fuciformis Pink patch—Limonomyces roseipellis
Susceptible Turfgrass: All turfgrasses, but particularly severe on fine-leaf fescue, and perennial ryegrass
Symptoms: Red thread causes patches that are reddish-brown in color and 1 to 4 inches in diameter up to 2 feet. Pink patch causes a gelatinous mass of pink mycelium with water-soaked leaves.
Conditions Favoring Disease: Red thread thrives in temperatures between 40°F to 85°F and in locations that are low in nitrogen. It also occurs in areas that experience more than 10 hours a day of foliar wetness for several consecutive days.
Pink patch usually develops in the presence of red thread. These two similar diseases often occur under the same conditions and at the same times. It is distinguished from red thread by the absence of “red threads,” or sclerotia.
- Mow turf frequently and collect clippings to remove diseased portions of the leaves.
- Maintain adequate nitrogen and a balanced fertility.
- Apply moderate to high amounts of phosphorous and potash.
- Maintain the soil pH between 6.5 to 7.0.
- Reduce shade.
- Increase the air circulation to the turf’s drying process.
- Irrigate turf deeply and as infrequently as possible.
- Use fungicides to control disease when it is a chronic problem.
Occasionally occurs in: Red Thread: AL, AR, AZ, CA, FL, GA, LA, MS, NM, OK, SC, TX.Pink Patch: AR, AZ, CA, NM, OK, TX.
Frequently occurs in: Red Thread and Pink Patch: CO, CT, DE, IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MN, MO, MT, ND, NE, NH, NJ, NV, NY, OH, OR, PA, RI, SD, UT, VA, VT, WA, WI, WV, WY.
Causal Agent: Sclerotium rolfsii Sacc.
Susceptible Turfgrass: Bentgrass, bluegrass, bermudagrass, ryegrass, and tall fescue
Symptoms: Most common in warm regions. Symptoms begin as yellow circular patches, becoming chlorotic, then reddish-brown. Patches become thin through the summer, with grass being killed in rings that may grow to several feet. Mycelium may be visible on the ring edges when moisture is present. White sclerotia are produced in large numbers on dead grass, becoming yellow-brown with age. Frog-eye or crescent- shaped patches are common.
Conditions Favoring Disease: Sclerotia germinate above 75°F. Disease is most severe at 77–95°F. Day temperatures above 85°F and nighttime temperatures above 70°F favor southern blight development. Disease is most severe under hot, moisture saturated conditions such as wet weather following a drought period. Soils with pH below 6.5 and soils with high organic matter also encourage this disease. Mycelium move rapidly and extensively through thatch or soil, and are easily spread to non-infected turf.
- Reduce thatch by verticutting or core aerification.
- Lime to raise pH above 7.
- Ammonium sulfate on greens and tees as a nitrogen source.
- Apply registered fungicides on a preventive basis.
Occasionally occurs in: CO, DE, KS, KY, MD, MO, NV, UT, VA, WV.
Frequently occurs in: AL, AR, AZ, CA, FL, GA, LA, NC, NM, OK, SC, TN, TX.