SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/107950
FieldScience >> FIGURE 3. Differential tall fescue response after covering for 6 days in the fall with Matrax/Terratrak (top) or Plywood+Enkamat (bottom) (photo courtesy of John Royse). >> FIGURE 4. Spring Dead Spot on a Riviera bermudagrass athletic field in Rocky Mount, VA (photo courtesy of David McCall). ucts allowed 5 to 25% of photosynthetically active radiation through to the leaf blades when measured at solar noon. During cooler spring and fall periods this resulted in almost complete turf persistence and recovery even when covered for the entire 20-day test period, while both plywood treatments allowed for only 5 days of cover. During summer, extra light transmission through Terratile resulted in significantly higher temperatures reducing turf persistence to 10 days compared to 12 days for Matrax. Plywood or plywood over Enkamat resulted in almost complete turf death after only 2-4 days of cover in the summer. Our results were clear and consistent: Use of a rigid cover that allows some photosynthetically active light to reach the turf canopy is of primary importance, with air exchange and compression resistance being important, but secondary. SPRING DEAD SPOT SDS MAN AGEMENT IN BERMUDAGRASS – David McCall. David is a research associate and PhD candidate in the Plant Pathology, Physiology, and Weed Science Department of Virginia Tech. He has primary responsibilities in turfgrass pathology. In Virginia, where a growing number of athletic facilities have transitioned to improved varieties of bermudagrass, the most frequent disease-related question I hear is "What can I do about my Spring Dead Spot?" As most who have managed bermudagrass know, spring dead spot (SDS) is the most common and damaging disease of bermudagrass (Figure 4.). Not only is the disease highly unsightly, but a se- 18 SportsTurf | February 2013 vere patch can be depressed to bare ground, often half an inch or more below the surviving turf stand. This can play havoc on playability and increase the chance for athlete injury. For decades, a standard recommendation for suppressing SDS has been to use ammonium sulfate as a primary nitrogen source throughout the summertime. This was based on research on one of the pathogens, Ophiosphaeralla herpotrica, which is most commonly found throughout the Great Plains and other Midwestern states. The general belief was that all species of the causal agent (there is also O. korrae, most common in Southeastern US, and O. namari, most common in Australia and New Zealand) would respond the same to nitrogen sources. However, research from the turfgrass pathology program at North Carolina State clearly demonstrated that O. herpotrica and O. korrae responded differently when clean bermudagrass was inoculated. O. herpotrica responded as expected, and was suppressed with ammonium sulfate. O. korrae, on the other hand, did not respond to this, but did to calcium nitrate. While the impact on disease activity is not fully understood for each species, we do know that sulfur-based nitrogen sources will lower pH in the upper rhizosphere, and most nitrate sources have little effect on pH. Because of the widespread problem for turf managers in Virginia, field research trials were initially established on sites with severe SDS epidemics in the spring of 2010 to see how quickly this new guideline may reduce disease. Trials were established on one soccer field (Southwestern Virginia), two golf course fairways (Central Virginia and the Eastern Shore), and one research plot at the Hampton Roads AREC in Virginia Beach. Plots with pre-existing SDS were fertilized with ammonium sulfate (21-0-0), calcium nitrate (15.5-0-0), or soluble urea (46-0-0). Two additional management strategies were applied to test confounding effects of nitrogen source. Plots were split to test whether fall applications of fungicides can speed the recovery of SDS. Interaction with late summer vertical mowing was also examined. While the NC State research showed dramatic results for new patch development, incorporating various nitrogen sources into pre-existing conditions in our trials has not Table 2. White grub counts in 2011 Turfgrass Soil Insecticide Efficacy Trials, Tazewell Co., VA. Treatment/Formulation/ Application Timing1 Application rate (amt product/acre) White grubs per sq ft (± SEM)2 Untreated check — 24.13 (3.48) a DPX-HGW86 20 SC April 8.0 fl oz 23.25 (5.22) a Merit 75 WP April 6.4 oz 22.00 (4.26) a Zylam 20SG July 32.0 oz 19.00 (3.42) ab Allectus GCSC April 4.5 pints 9.00 (1.63) b Acelepryn 1.67 SC July 8.0 fl oz 2.00 (1.08) c DPX-HGW86 20SC July 8.0 fl oz 0.75 (0.48) c Acelepryn 1.67 SC April 8.0 fl oz 0.00 (0.00) c Merit 75 WP 6.4 oz 0.00 (0.00) c 1Early application: 20 April; late application: 19 July 2Means within a column followed by the same letter are not significantly different at P < 0.05 according to LSD tests. www.sportsturfonline.com