Spring Dead Spot
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April 10, 2017
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A chronic and difficult disease to control of bermudagrass is Spring Dead Spot (SDS). Spring dead spot symptoms appear in spring when bermudagrass begins growth or “green up”. These conditions exist in the United States in the northern range of bermudagrass adaptation. The circular patches of dead turfgrass normally 1 meter (3 feet) in diameter tend to reappear and expand in the same spot yearly. The turfgrass plants quickly slough-off causing the sunken patches. The patches can coalesce appearing as non-uniform areas. Three species of Ophiosphaerella - O. herpotricha, O. korrae, O. narmari – have been reported to cause spring dead spot. The pathogens of spring dead spot are considered ectotrophic root infecting (ERI) fungi. Species of Ophiosphaerella produce ectotrophic runner hypae along the surface of roots and stolons that lead to infection and eventually blackening and destruction of the root system.
These pathogens are thought to be most active in the fall and spring when the bermudagrass is either entering dormancy in the fall or breaking dormancy in the spring usually when soil temperatures are below 21 C (70F). It has been observed, and subsequently researched that freezing temperatures following pathogen infection and activity enhances symptom expression. Bermudagrass freeze tolerance is decreased by infection by these ERI fungi making winter injury a greater possibility.
Spring dead spot is control is difficult. Culturally, establishing cold tolerant varieties is probably the best practice. Studies have shown that potassium applications in the fall can reduce SDS damage, probably by enhancing the cold tolerance of the bermudagrass. If soil pH is high, try to lower the pH. Generally, the Ophiosphaerella species are suppressed in acid soils.
In the spring, once bermudagrass begins active growth, management practices that enhance turf recovery should be instituted. Fungicides are available that may control spring dead spot to some extent. Applications should be made a month prior to dormancy. Spring fungicide applications are ineffective.