Winter Springs Into Summer for Virginia's Turfgrasses

Erik Ervin Associate Professor, Turfgrass Science

It was interesting to spend some time talking with many of Virginia's turfgrass professionals at the 2005 Turfgrass Research Golf Tournament at Wintergreen Resort on Monday, June 6. Rarely do you get people that are so polarized in terms of their description of the growing conditions for the year to date. Clearly, the weather patterns for the first half of 2005 have resulted in some interesting challenges for many of Virginia's turfgrass managers, while others have reveled in the cooler than normal temperatures. In general, all turfgrass managers managing cool-season turfgrasses have loved life so far this year with the abnormally cool conditions being ideal for our bluegrasses, fescues, ryegrasses, and bentgrasses. The only limitation most cool-season turfgrass managers could identify to date is a rainfall deficit that ranges from 3-6 inches in the western half of the state. Still, since water is not a limiting factor (at least not yet) these managers have no major complaints regarding the moisture deficit because it has allowed them to manage soil moisture rather than Mother Nature (more on this later).

Managers of warm-season turfgrasses have been scratching their head on what they should be doing with their bermudagrass and zoysiagrass turfs. Glenn Rountree, ANR agent in Isle of Wight County, informed me that his part of the state is approximately 160 Heating Degree Days behind where they were at this time last year. Any way you slice it, this lack of heat can not be good for spring growth and development of warm-season plants.

What did bermudagrass do this spring? In most parts of the state it began greening in early April, but then it mostly sat there in some stage of partial greening/no growth for almost all of May. Finally, as we complete the first week of June, the state has actually had some weather conducive to warm-season turfgrass growth and we will likely be complaining about the heat, humidity, and lack of rainfall soon enough. I will never forget my good friend (and weed scientist) Dr. Euel Coats telling me that "bermudagrass doesn't start growing until you have to kick the covers off at night." He is absolutely right.

Here are some thoughts on what I view as the results/implications of this year's weather pattern to date as it applies to turfgrass management in Virginia:

The implications of the cool spring weather

1. It's been a great year for weeds. Winter weeds have thrived and the gaps in turf canopy coverage as weeds finally begin to die will only perpetuate weed control problems this year. The major concern voiced by all segments of the turf industry managing warm-season grasses in the Piedmont and Tidewater regions has been a serious breakdown in weed control. For many, the problem has been a combination of both an extended growing period for many of the winter annual weeds that have normally died by now and the breakdown in control of summer annual weeds due to a combination of heavy rainfall and slow growing turf (i.e. there is little warm-season turf canopy to block sunlight from reaching weed seed). You can anticipate more postemergent herbicide applications are needed now. Also, IF season-long weed control is required/expected, I anticipate that follow-up applications of preemergent herbicides will likely need to go out earlier than normal this season. Obviously, winter weeds have also been more competitive in cool-season turfs as well, so similar attention in weed control should be given here as well. This lack of weed control has been evidenced in ALL segments of the turf industry: golf, sports turf, home lawn care, and sod production. If challenged about "what happened?", turfgrass managers should tactfully remind their clientele that turfgrasses have good and bad periods due to Mother Nature that are no different from traditional row crop agriculture. There is always a need for continuing education! Use this article as a means of support for your explanation.
2. What about my spring fertility? If you have had above average rainfall it is likely that you have lost some of the nutrients your turf otherwise would have utilized. But your strategy on how to deal with this should primarily be based on the grass that you are growing. Warm-season grasses will just now begin to respond to N fertility due to the more favorable environment. It is now appropriate to initiate N fertility programs that optimize growth and development characteristics of warm-season grasses. Cool-season grasses should have had their spring fertility needs already met by now and further N applications are discouraged until late summer/early fall.
3. Winter overseedings of ryegrasses are transitioning out VERY SLOWLY. Is this good or bad? It depends on your perspective. There is some beautiful overseeded grass around the state, but for as great as this particular grass looks, you can bet that the bermudagrass is struggling that much more. What has already been a slow year for bermudagrass is further compounded by the competition from the overseeding grass that has thrived in these cooler than average temperatures. On the campus of Virginia Tech we have witnessed a very much unexpected lack of control of the perennial ryegrass overseeding on Worsham Field with one of our best chemical transition tools. Even though RevolverŠ (foramsulfuron) was applied at the maximum label rate just before graduation exercises in mid-May, the ryegrass was not controlled as of the first of June. Dr. Askew has recommended a repeat application of Revolver for ryegrass control and anticipates with the current warm temperatures that control won't be an issue this time. However, the repeat application has delayed Athletic Facilities' Manager Casey Underwood's planned sprigging dates to aid the bermudagrass recovery in heavily worn areas of the field (there is a 2-week window between Revolver application and sprigging). Any others had similar problems/concerns with chemical transition of overseeding turf this year?
4. Disease pressure to date has been somewhat reduced. Research Associate David McCall has indicated to me that there have been numerous sporadic reports of some pretty heavy early attacks of dollar spot, but they have not yet been widespread in nature. Rhizoctonia and Pythium blight have not been major concerns on any of the grasses to date, but expect these pressures to ramp up significantly with this first blast of summer-time weather in June. I have always found it useful to begin paying serious attention to disease pressure for most of the problematic turf diseases when the sum of maximum daytime highs and relative humidities is greater than or equal to 150. I know that many of my plant pathology colleagues have more precise prediction models and rules of thumb than these, but I have always found this simple "150 rule" to be pretty representative of the warm, moist conditions under which we start to realize some of our greatest disease pressure. We've just begun encountering these temperature and humidity ranges, so expect disease pressure to increase on all grasses.
5. What if your climate has been abnormally cool AND wet? This primarily applies to cool-season turfgrass managers growing turf on sand-based soils. Something to pay attention to is the depth of your roots as summer temperatures and weather patterns approach. As I mentioned earlier, most folks managing cool-season turf in the western half of the state where it has actually been drier than normal have been able to "force" their roots deeper into the soil by carefully managing water amounts. If you've been cool and wet, don't be lulled into a false sense of security. As weather patterns finally change and we become "hot and dry" you can anticipate more moisture stress because of a more limited root system.

These are just a few of the items that have been (or will be) concerns this season. Consult www.vtturf.com for a complete listing of VCE turfgrass publications that address specific needs of turfgrass management in Virginia.

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