Spring dead spot (SDS) is one of the worst diseases a superintendent can face while growing bermudagrass in the transition zone.

Arguably beautiful to a turf pathologist, these spring dead spot symptoms are ugly from both the golfer's and the superintendent's perspectives, and they reduce playing surface quality.

SDS injury usually takes the form of circular dead areas that can range from a few inches to several feet in diameter. Patches can coalesce into even larger areas at times. While the fungi that cause SDS may be colonizing the plants in summer, fall or even winter, the injury symptoms occur during green-up in the April-May period. The disease is most common on mature bermudagrass stands that are 2 or more years old.

Survival of bermudagrass crowns and rhizomes within the infected patches is highly variable, ranging from nearly complete survival to no survival. Often winterkill and SDS interact to cause devastation. Besides being very unsightly, SDS patches are usually sunken, providing a less-than-optimal ball lie for golfers. As the season progresses, weeds often proliferate in the patches, further reducing the quality of the playing surface.

SDS is caused by at least three different species of fungi.Ophiosphaerella korraeis the most frequently isolated SDS pathogen in the southeastern United States (Iriarte et al. 2004; Wetzel, Skinner, and Tisserat, 1999) whileO. herpotrichais the most abundant SDS pathogen in Kansas and Oklahoma (Tisserat et al., 1989; Wetzel, Skinner and Tisserat, 1999).Ophiosphaerella narmarihas been isolated as a casual agent in California, Kansas, Oklahoma and North Carolina (Iriarte et al. 2004; Wetzel, Hulbert and Tisserat, 1999).

An integrated approach to managing SDS involves the 1.) selection and use of resistant cultivars, coupled with practices that 2.) expedite bermuda growth into damaged areas that 3.) reduce the severity of the disease in the future (Tisserat, 2004; Martin and Hudgins, 2002).

In field tests, the outer two holes received inoculum while the center hole was used as a check to assess injury from removal of a plug late in the growing season.

More specifically, the practices shown to reduce severity of the disease include combinations of aeration and vertical mowing performed twice each year to reduce soil compaction and thatch mass (Fry and Tisserat, 1997) as well as the use of acidifying fertilizers (Dernoeden et al, 1991) that may neutralize soil alkalinity. Surprisingly, while SDS has been connected with intense management practices, close mowing alone does not increase the severity of the disease (Martin et al, 2001).

Many practicing turfgrass managers consider any cultural practices that reduce winter-hardiness as initial "suspects" in further increasing severity of SDS until those practices are found "not guilty." This is because the actual mechanism of bermudagrass death with this disease is believed to be low-temperature kill on plant material that was pre-disposed by fungal infection. One such "suspect" practice is late-season nitrogen fertilization.

It is important to note that it has not been established through research that late-season fertilization of bermudagrass increases SDS severity. Furthermore, recent work at other universities has shown that late-season fertilization does not necessarily increase winterkill.

Overall, control of SDS with fungicides has been erratic from state to state and trial to trial. Tredway and Butler (2003) recently provided a review of their initial encouraging fungicidal results on fungicide choice, carrier rate and the importance of timing of applications in the late summer through fall. Biocontrol agents are currently under study by members of our team and control of SDS may be a possibility in the future (Anderson et al., 2003).

Although proper cultural techniques are critical to a successful SDS management program, use of resistant cultivars is arguably the foundation of a successful program in situations where managers can influence the cultivar being installed initially or through renovation. With this in mind, a substantial amount of screening for SDS resistance was conducted in the mid-continent during the 1990s, with work continuing today.