Spring Dead Spot Information
Causal Agent(s)
- Ophiosphaerella korrae
- Ophiosphaerella herpotricha
- Ophiosphaerella namari
Hosts
- Hybrid bermudagrass
- St. Augustinegrass
- Zoysiagrass
Symptoms & Signs
Symptoms manifest in the spring as winter kill when infected turf exits dormancy. Spring dead spot symptoms appear as necrotic rings or patches ranging from 6 inches to 2 feet in diameter. Patches may also coalesce across larger areas. Taking a soil core from within a patch will show compromised root systems that are dark, rotted, and shallower than surrounding healthy turfgrass.
Images of spring dead spot symptoms:
When Does it Occur?
Infection occurs in the fall when soil temperatures drop below 70° F. After infection, the pathogen compromises the root system, predisposing the infected turfgrass to death from winter stress. Spring dead spot recurs in the same locations from year to year. Typically, it takes around 3 years for spring dead spot to start occurring in new turfgrass stands.
Cultural Management
Using more cold-tolerant cultivars of hybrid bermudagrasses can reduce symptom severity. Avoid excessive N applications in the fall. Reduce thatch accumulation through aerification and verticutting. Topdress putting greens to further dilute thatch accumulation. Calcium nitrate can reduce damage from O. korrae, but ammonium sulfate was more effective at suppressing O. herpotricha. Submitting samples to a diagnostic lab for identification is recommended to make more informed management decisions.
When symptoms are visible in the spring, regrowth into affected patches is the only way to recover. Thoroughly cultivate dead areas to break up mats of dead material and to encourage lateral spread of healthy turfgrass. Regrowth into dead areas may be inhibited by the use of some herbicides.
Chemical Management
Preventative applications are the only way to manage spring dead spot. They should be made in the fall when soil temperatures drop below 70° F for 5 consecutive days. In general, two applications 28 days apart can provide good control of spring dead spot. Immediately apply 1/8” of irrigation after fungicide applications to move the product into the root zone. Recent research suggests some differential suppression between O. korrae and O. herpotricha, underscoring the importance of identifying the predominant species at a site.
