Research Articles continued
REDUCING PESTICIDE INPUTS WITH COMBINATIONS of Tall Fescue and Hybrid Bluegrass Virginia Tech Researchers: Matthew Cutulle, Graduate Research Assistant; Jeffrey E. Derr, Ph.D., Professor of Weed Science; and Adam E. Nichols, Research Assistant (Virginia Tech’s Hampton Roads Agricultural Research and Extension Center), with Brandon Horvath, Ph.D., Assistant Professor of Plant Pathology (University of Tennessee) Sponsors: The Virginia Turfgrass Foundation and The Virginia Agriculture Council
In
the transition zone, tall fescue can be used in multiple situations, such as home lawns, athletic fields, golf course roughs and other low-maintenance turfgrass areas. Tall fescue exhibits adequate shade tolerance, is adapted to a wide arrange of soils and can be cut at 3.8 cm or more. Characteristics that favor its use among homeowners include its drought tolerance, insect resistance, high turf density and relatively low fertilizer requirements. Tall fescue, however, is susceptible to brown patch (Rhizoctonia solani), which is aesthetically unpleasing and can thin out the turfgrass stand, leading to the encroachment of undesirable weedy species. Hybrid bluegrass cultivars, from crosses between Kentucky bluegrass (Poa pratensis) and Texas bluegrass (Poa arachnifera), may be an alternative. Hybrid bluegrass has the desirable qualities of Kentucky bluegrass (i.e., color, brown patch resistance and quality) but was bred to have increased
heat and drought tolerance. However, hybrid bluegrass requires more fertility and may not establish as quickly as tall fescue. We hypothesize that combining hybrid bluegrass (which is resistant to brown patch) with tall fescue (which establishes quickly) will reduce overall disease severity and weed encroachment, thus leading to reduced fungicide and herbicide inputs while maintaining turf quality.
Our research Plots of ‘Greenkeeper’ tall fescue and ‘Thermal Blue Blaze’ hybrid bluegrass were seeded with four treatments: (1) 6 lbs./1,000 ft2 Greenkeeper alone, (2) 2.25 lbs./1,000 ft2 Thermal Blue Blaze alone, (3) 5.4 lbs./1,000 ft2 Greenkeeper with 0.6 lbs./1,000 ft2 Thermal Blue Blaze, and (4) 3 lbs./ 1,000 ft2 Greenkeeper with 1.13 lbs./ 1,000 ft2 Thermal Blue Blaze. These plots were established in fall 2006 and fall 2008 at Virginia Tech’s Hampton Roads AREC in Virginia Beach, Vir-
Treatment
Seeding rate (lbs./1,000 sq. ft.)
Percent turf cover November 2006
Percent brown patch August 2009
Percent Persian speedwell cover November 2009
1) Tall fescue
6
70%
40%
13%
2) Hybrid bluegrass
2.25
40%
3%
13%
3) Tall fescue + hybrid bluegrass
5.4 + 0.6
69%
12%
6%
4) Tall fescue + hybrid bluegrass
3+ 1.13
61%
8%
5%
9
8
4
LSD 0.05
Table 1. Effect of seeding combinations on turf cover, brown patch and Persian speedwell density. 20 | VIRGINIA TURFGRASS JOURNAL May/June 2010 www.vaturf.org
ginia. All plots were mowed at 4" and received 3 lbs. N/1,000 ft2 per year. Percent turfgrass cover, weed cover, brown patch severity and tiller counts were taken throughout the year. No preemergence herbicides were applied to this trial.
Research results Tall fescue germinated quicker than hybrid bluegrass, achieving 70% cover at one month after seeding, while hybrid bluegrass cover was only 40%. At one month after seeding, percent cover by purple deadnettle, common chickweed and henbit were greater in hybrid bluegrass alone compared to tall fescue alone. Weed cover in the combination seeding #3 was similar to that seen in tall fescue alone. Weed cover in the combination seeding #4 was intermediate between the two monocultures. Monoculture stands of hybrid bluegrass had the highest cover of southern crabgrass in the summers of 2007 and 2008, and the highest cover of white clover in the spring of 2008. Under the fertility level in this program, the monoculture of hybrid bluegrass was never able to recover from slow establishment, resulting in higher weed density. Weed cover in the combination seeding treatments was similar to that seen in monocultures of tall fescue. Brown patch infestations in the summer of 2008 were highest in the monoculture of tall fescue. In August 2009, plots seeded with only tall fescue had significantly more brown patch than the other seeding treatments. The high brown patch severity observed in