Red Thread is a foliar disease that usually occurs on taller mown turfgrasses during spring and fall. The effects of the disease are largely cosmetic: crowns and roots are not infected, therefore plants are not killed, and the turf eventually will recover. Red thread symptoms contribute to a generally undesirable appearance. Red thread takes its name from the antler-like structures (sclerotia) produced by the fungus (Laetisaria fuciformis) on the tips of affected leaf blades. The red or pink sclerotia are apparent without magnification and are useful in the identification of the disease in the field. From a distance, red thread symptoms appear as circular patches of tan or pink turf ranging from 4” – 8” in diameter. Kentucky bluegrass, perennial ryegrass, and tall fescue are most commonly affected by red thread.
Occurrence -
Red thread development is favored by poor turfgrass nutrition and other factors that promote slow growing turf. Deficient levels of nitrogen fertility can promote serious outbreaks. Disease development occurs over a relatively wide range of cool, mild conditions (40 ° – 70 ° F), typically in the spring and fall of the year, especially when long evening dew periods occur.
Non-Chemical Control - Genetic resistance to red thread infection is limited. The most important non-chemical (cultural) control
option involves the implementation of an adequate
and balanced nitrogen fertility program. A good
fertility program implemented over two to three years
will drastically reduce or eliminate further red thread
problems. Other cultural practices that keep turf
healthy and vigorously growing also help suppress
red thread. Also, avoidance of irrigation practices
that extend dew periods (late afternoon, early
evening) will contribute to a reduction in red thread
outbreaks.
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Chemical Control - Fungicides are not advised for red thread control on
home lawns for various reasons. A red thread outbreak
signals a more immediate problem with the
health and vigor of the lawn. In almost all cases,
practices that result in a well-nourished lawn also will
result in suppression of red thread development.
Also, most effective chemicals are not labeled for use by home owners and are difficult to apply properly. A licensed professional
applicator should be used to apply most fungicides, thereby increasing treatment costs. Finally, the turf will recover
to some extent with even a modicum of care because
red thread does not affect the turfgrass crowns and therefore usually does not kill the plants.
Text courtesy of: Philip Harmon and Dr. Richard Latin, Purdue University |
