Spring Dead Spot
In the transition zone, fall is a time when spring dead spot (SDS) pathogens infect Bermudagrass root systems. On Bermudagrass golf course fairways and athletic fields, spring dead spot is a devastating disease. Symptoms appear as the name implies. Patches ranging from six inches to over a yard in diameter appear as the Bermudagrass breaks spring dormancy. The patches appear sunken down into the turf. This disease appears in the same areas from year to year with increasing severity. If the disease progresses over a period of years the patches coalesce and the damage appears more like winter kill.
Figure 1. Early spring symptoms of Spring dead spot.
Damaged areas are slow to recover with the potential injury remaining visible through the summer. The pathogens associated with the disease are Ophiosphaerella korrea and O. hepotricha in the United States and O. namari, along with O. korea in Australia. The pathogens infect Bermudagrass below ground attacking the roots, rhizomes and stolons during the fall and winter. Ophiospherelia species infect Bermudagrass roots and stems when soil temperatures are between 50 and 77 °F. Maximum infection occurs at 59 °F.
Syngenta offers automated alerts to make it easier to monitor soil temperatures in your area. Sign up at GreenCastOnline.com/soiltemperature.
While cool soil temperatures are ideal for Ophiospherella infection they are not for Bermudagrass growth. The pathogens weaken the plants making them more susceptible to cold and freeze injury. What is going on in the fall with infection is not visibly evident until early spring.
Figure 2. The circular patch symptoms of spring dead spot are often colonized by weeds. In this case Poa annua is the primary weed along with dandelion.
Injury from spring dead spot often lingers through the summer and into early fall. Poor soil conditions (compaction, thatch, poor water infiltration, etc.) enhance disease severity. Coring practices multiple times through the growing season can help reduce soil compaction and thatch accumulation.
Figure 3. Spring dead spot (SDS) is a devastating disease that can linger through the summer. In the above photograph the early spring symptoms of SDS have lingered through the summer in North Carolina.
Cultural practices to reduce the severity of spring dead spot include fall applications of potassium to reduce SDS by enhancing the cold tolerance of Bermudagrass. Lowering the soil pH on alkaline soils reduces the severity of SDS. The impact of lowering soil pH is likely pathogen species specific. Ophiosphaerella korrea is more responsive to treatments lowering soil pH than O. hepotricha. Where spring dead spot occurs nitrogen fertilization should cease approximately two months prior to bermudagrass entering dormancy.
Figure 4. Spring dead spot occurs globally on bermudagrass turf. The photograph above was taken at a golf course in Portugal in June.
Chemical control in the form of fungicides should be targeted when the pathogen is attacking the Bermudagrass roots and stems. A general recommendation is to make treatments in the fall when soil temperatures are between 60 and 80 °F. Where severe disease pressure occurs, multiple applications are often required. It is important to note where SDS symptoms develop in the spring. Come fall these areas will need to be treated.
Fungicides recommended for SDS control include Posterity®, Velista®, and Headway®. Following application, apply immediately at least a ¼ inch of irrigation.
For additional information on SDS and other root pathogens see this Field Insights Blog post or download this solutions sheet.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: