Predisposing Conditions:
- water-saturated environment associated with rainy weather
- slow shoot growth caused by nitrogen deficiency or water stress (although the disease also may develop in well-fertilized turf)
Symptoms and Signs:
- tufts of pink or reddish web-like fungal growth can be seen on leaves, sometimes binding leaves together
- infected leaves may appear water-soaked
- leaves eventually become blighted, appearing a bleached tan color
- bright red fungal structures, called "red threads" (approx. ¼ inch or less long), can be observed extending from leaf surfaces, particularly the cut ends of the grass blades
- affected areas initially are 1-2 inches, but may coalesce and form irregular shapes
- dead leaves often are interspersed with green leaves
Biology of the Disease
- caused by Laetisaria fuciformis, a fungus
- infection occurs on the leaf and stem parts, not the roots
- rarely kills plants, but does weaken turfgrass, contributing to decline from other stresses
- spread by water splash, wind, mowers, shoes, and other mechanical means
- red threads, when dry, function as survival structures (sclerotia), allowing the fungus to survive from season to season
Control
- maintain adequate fertility
- raise the mowing height, if possible
- avoid mowing early in the morning when the turf is wet with dew
- avoid frequent sprinkling in the late afternoon
- collect grass clippings when red thread is active to reduce the number of red threads that fall back into the turf
- a fungicide program may be necessary on turf with a history of red thread
- labeled products include Banner, Cavalier, Chipco 26019, Cleary’s 3336, Compass, Dithane, Fore, Heritage, Junction, Mancozeb, Pentathlon, Protect T/O, Rubigan, and others