Grady Miller, Casey Reynolds, and Scott Brinton
Once again Mother Nature seems to be causing problems with our warm season grasses in NC, particularly overseeded bermudagrasses in the piedmont.
The above average February and March temperatures initiated early bermudagrass green-up. These warmer than average months were followed by below average temperatures in April, May, and June (see Figure 1) resulting in a late-spring growth surge in overseeded ryegrass. While this provided nice ryegrass surfaces, it caused an increase in shading and competition to the bermudagrass.
The mild winter temperatures resulted in less winterkill compared to previous years. Non-overseeded bermudagrass seems to have come out of the winter in better than average shape. But that which was overseeded has fared much worse compared to previous years.
Poor green-up has been even worse on athletic fields in areas that were painted (lines and logos). Good painting practices often results in mild thinning of turfgrasses in painted areas. Repeated paint applications during a fall season can lead to more chronic stress and additional thinning. The problem this year has been the combined effects of shading by ryegrass and the added stress of the paint. Pigments in the paint, particularly darker colors, absorb light reducing sunlight available for photosynthesis.
The cooler temperatures combined with the impact of shading from ryegrass (and paint in some cases) has slowed bermudagrass recovery resulting in prolonging the ryegrass/paint shade effects.
So, what is the answer? Generally, all the site needs is a little time and warmer weather combined with reasonable fertility/irrigation practices. Of course that may not be the case for every situation. Bermudagrass needs 8 hours of full sun and warm temperatures for optimum growth. If the turf is just off-color or just slow to become dense, then it should continue to regrow from rhizomes and stolons becoming denser with time. If there is no turf growth and the damage is relatively small, the turf may fill-in from stolon and rhizome growth from around the edges. If the damaged area is extensive, then it will require taking plugs from healthy areas and transplanting within the damaged turf or re-sodding.
Figure 1. Average Daily Temperature in Raleigh, NC in February through June from 2008 – 2011 compared to 2012.
Figure 2. Overseeding trial of multiple cultivars in foreground and non-overseeded bermudagrass in background taken May 29, 2012 in Raleigh. Note the variation in green-up and ryegrass retention among overseeded ryegrass plots within the overseeding trial.