Once the overseeded stand of ryegrass dies, a soil crust may form where the bermudagrass understory is thin.During recent golf facility visits in southern Arizona, it was surprising to see how overseeded ryegrass populations continue to linger despite near record high temperatures. The longer the ryegrass persists, the less time bermudagrass has to recuperate from winter overseeding. Golf facilities need to act quickly over the coming weeks to remove the ryegrass and stimulate active bermudagrass growth. The following strategies have been effective throughout the Southwest region:
- Don’t turn off the water! Although reducing irrigation in late June/early July will eventually kill the ryegrass, it will also delay bermudagrass recovery.
- Consider a low or medium rate application of one of the popular sulfonylurea herbicides to chemically remove the ryegrass. With the prevailing hot weather, these herbicides will be very effective.
- Scalp the ryegrass to a height of 0.300 to 0.375 inches to allow more sunlight into the turfgrass canopy and help stimulate bermudagrass growth.
- Use a vertical mower, flex-tine harrow, road broom, or a combination of these tools to remove the dead and decaying ryegrass. Furthermore, it is important to use these tools to reduce/prevent the formation of a soil crust that is created once the ryegrass dies, which restricts bermudagrass growth and recovery.
- Apply generous amounts of nitrogen fertilizer where bermudagrass growth is weak. Apply 0.5 to 1.0 pounds of soluble nitrogen per 1000 square feet each week until bermudagrass recovers.
- Temporarily close the golf course. Many have been able to expedite bermudagrass recovery by closing the golf course for several weeks, which allows the agronomic staff to aerate, mechanically remove the dead ryegrass and, most importantly, water the golf course throughout the day.
- Water generously. Although applying water during the day may seem wasteful to on-looking golfers and homeowners, it is often impossible to apply enough water during the night to fully meet turf water requirements. The focus must be on stimulating the recuperating bermudagrass, and such a task requires adequate soil moisture. One unique tactic shared by a superintendent is to remove the internal sprinkler assembly and turn on the valves, which eventually floods the entire fairway. This strategy only works where the fairways are flat, but this superintendent noted that bermudagrass always recovers faster on these fairways than others where overhead irrigation is used.
- Lastly, a growing trend to aid bermudagrass transition is to apply 10 to 40 tons of sand per acre to the fairways. The sand helps to minimize or prevent the soil crust (that forms from decaying ryegrass) that discourages bermudagrass growth. Not only will sand topdressing aid bermudagrass growth, but over time will improve soil conditions as well.
- A webcast by John Foy titled Winter Overseeding Transition Management further explains the strategies offered in this update.
Information on the USGA’s Turf Advisory Service
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