It’s generally not this late in the season before spring dead spot (SDS) is discussed on Course Consulting Service visits. The weather this spring has been unusually cool and cloudy, so the symptoms of SDS took longer to become visible. The irregularly shaped patches are often noticeable in early May with typical spring weather conditions.
While the name spring dead spot indicates when the disease symptoms are evident, control strategies are necessary in the fall before the fungus is active and able to attack the roots, rhizomes and stolons of bermudagrass. Since the fungus is attacking roots, it makes plants more susceptible to freezing injury, which is why it is often more severe in the northern areas where bermudagrass is planted.
If your course is experiencing SDS now, management practices should focus on growing healthy bermudagrass. As the surrounding grass grows stronger, it will spread to fill in the patches. Normal bermudagrass management like slicing, verticutting and adequate fertilization are necessary.
As you plan for preventative strategies this fall, there are a few key points to remember. First, preventative control products only suppress the fungus. Applications are most effective when air temperature is around 70 degrees Fahrenheit, or soil temperature is between 60 and 80 degrees Fahrenheit. That said, there is new evidence from Virginia Tech showing that holding applications until air temperature is closer to 65 degrees Fahrenheit might provide better control. Two applications about 28 to 30 days apart will extend the window of efficacy.
The second point is cultural management. Reducing thatch and removing clippings so that they do not accumulate at the surface will help limit SDS. Alleviating compaction with aeration and vertical mowing is also recommended. Lastly, do not apply nitrogen within six weeks of the onset of dormancy.
Spring dead spot is a frustratingly difficult disease to control. Despite good research on the fungus, and many years of field observations, superintendents still struggle to get their hands around this disease. One year it seems control was great, so you do the same thing the next year and have less than acceptable results. Good plant health and a favorable growing environment with minimal thatch and good drainage are needed anyway and will help reduce SDS.
Northeast Region Agronomists:
Adam Moeller, director, Green Section Education – amoeller@usga.org
Darin Bevard, senior director, Championship Agronomy – dbevard@usga.org
Elliott L. Dowling, senior consulting agronomist – edowling@usga.org
John Daniels, agronomist – jdaniels@usga.org