SUMMER SPOILERS OF 2010
It’s been a Challenging Summer for Lawns
2010 has been a particularly hot and brutal year for turfgrass managers in the Midwest. Lawns and athletic fields have been inundated with weeds and many have lost grass cover due to excessive heat and stress. The following article has been produced by the turfgrass science team at The Ohio State University to address some of these issues. THE EFFECTS OF HOT WEATHER ON COOL-SEASON TURF Cool-season turfgrasses prefer to grow in air temperatures between 60-75 degrees F and soil temperatures between 50 and 65 degrees F. While it is not uncommon for temperatures in Ohio to exceed these limits each summer, 2010 has been particularly challenging. A summary of air temperatures for both 2009 and 2010 can be seen in Table 1. In addition, it is important to note that the average soil temperature this year, at the 2” depth, was consistently above 70, increasing soil temperatures were above 70 by mid-June into July, and only got slightly above 80 in August.
The higher day and night-time temperatures relative to most years resulted in significant stress on both the shoots and root system of all our typical cool-season grasses like Kentucky bluegrass, perennial ryegrass, fine fescue and bentgrass. Most people forget that the underground root system of turfgrasses is the key for absorbing nutrients and water. At soil temperatures above 75 F the roots of cool-season grasses begin to slow in growth and become less physiologically active, resulting in the onset of the “hidden turfgrass stress” called root dysfunction. At the reported soil temperatures in late June to late August (greater than 80 F) roots actually began to become dysfunctional, decline, and dieback causing additional overall turfgrass stress. The high (stifling) humidity and high temperatures both DAY and NIGHT resulted in doubling of turfgrass stress. Normally, cooler, less humid nights helps the turfgrass plant rebound from the daytime stresses. The turfgrass plant did not get this environmental nighttime rest period. The weakened turfgrass plant was more susceptible to heat stress, disease and weed invasion (i.e. crabgrass). Adequate rain during the summer in most areas of Ohio increased the potential for more weeds.
- The Ohio State University Turfgrass Science Team