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Spring Dead Spot Control in Hybrid Bermudagrass

Spring seems like a long way off, but now is the time to prevent your bermudagrass turf from looking like this upon greenup in the spring. Spring dead spot, caused by Ophiosphaerella korrae, can cause severe and long-term damage to bermudagrass on greens, fairways, roughs, athletic fields, and highly maintained landscapes if it is not properly managed.

There are many things that can be done to help reduce spring dead spot development. Probably one of the most effective practices is hollow-tine aerification. In the picture to the right, look how severe the disease is on the recreational area to the right as compared to the soccer field on the left. What's the difference? The soccer field was hollow-tine aerified three times in the previous year, whereas the surrounding areas were not.

In the Eastern United States, most people have good success in controlling spring dead spot with 1 or 2 fungicide applications in the fall. We've found that these applications are most effective when average daily soil temperatures are below 80 degrees and above 60 degrees.

The Midwest is a completely different story, however, as fungicides generally don't work very well against spring dead spot in that part of the country. Some have theorized this is because spring dead spot is actually caused by a different pathogen in the Midwest, where Ophioshpaerella herpotricha is most widespread. However, we've had great success in controlling O. herpotricha with fungicides in North Carolina in the few locations where it is present, so I tend to believe that different soil properties are responsible for the control difficulties observed in certain regions. Just keep in mind that what we find to work best in the Southeast isn't guaranteed to work everywhere.

Over the last 8 years, Rubigan has been the most effective and consistent fungicide for spring dead spot control in our trials. In fairways and athletic fields, we have seen excellent control from 2 applications (30 days apart) at 4 fl oz/1000 ft sq or a single application at 6 fl oz/1000 ft sq. On putting greens, which tend to be more susceptible to spring dead spot, I would recommend a total of 12 fl oz/1000 ft sq applied as either three 4 fl oz applications or two 6 fl oz applications.

Regardless of the program that you select, is critical that all of the applications are made before average daily soil temperatures dip below 60 degrees. This is the point at which bermudagrass plants start to shut down, and after this point the fungicide will not be absorbed and translocated in the plant.

There are other options for spring dead spot control. While Rubigan has been most consistent in our studies across a number of locations, we have also seen good to excellent control from Banner Maxx (2 applications at 4 fl oz), Headway (2 applications at 3 fl oz), and Eagle 20EW (2 applications at 2.4 fl oz) in some studies. Heritage has not provided effective spring dead spot control in our studies.

With any fungicide application for spring dead spot, it is very important that you water the fungicide into the root zone for best results. The pathogen is attacking the roots, rhizomes, and stolons of the bermudagrass plant, so that is where the fungicide needs to be. Most fungicides are absorbed quickly by the foliage, so irrigation must be applied right away before the spray dries on the leaves. On putting greens and fairways, typically 1/8" of irrigation is sufficient, but up to 1/4" may be needed on higher cut areas.

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