Research Summary
Preemergence Crabgrass Control in Tall Fescue Virginia Tech Researchers: Jeffrey Derr, Ph.D., Professor of Weed Science, and Adam Nichols, Research Assistant, Hampton Roads Ag. Research and Extension Center, Virginia Beach
temperature; 47% relative humidity; 5% cloud cover; wind 9 MPH NNE. Rain 1 DAT. Application B, 5/15/15 — 72°F air temperature; 62% relative humidity; 30% cloud cover; wind 8 MPH E. Irrigated 5 hours after treatment.
Research results a given product. We included Specticle FLO in the study as it had been suggested that tall fescue could tolerate this herbicide. We applied Tenacity either once or twice to see if applications at 8 fluid ounces per acre (0.25 pounds active ingredient/acre) could provide acceptable crabgrass control.
Our research Application A, 3/18/15 — 42°F air
Specticle injured and thinned tall fescue. At least in this study, tall fescue did not have acceptable tolerance to Specticle. Both single and split applications of Dimension, Barricade and Pendulum and the single application of Specticle gave good to excellent crabgrass control. The split application of Specticle and both treatments of Tenacity gave lower crabgrass control than the other treatments. Tenacity does not have the length of control as the other products tested. c
6 7 8 9
Specticle FLO 9 fl. oz./a A
10
Tenacity
11
Tenacity LSD P = .05
0.25 lb. ai/a AB 0.25 lb. ai/a A
Sept. 24, 2015 190 DAT1 / 132 DAT2
Treatment
68%
1
0%
5%
3%
2
0%
4%
5%
3
0%
5%
8%
4
1%
5%
4%
5
0%
1%
2%
6
0%
5%
4%
7
1%
19%
16%
8
3%
6%
3%
9
Untreated 0.25 lb. Dimension ai/a AB 0.5 lb. Dimension ai/a A 0.38 lb. Barricade 4F ai/a AB Barricade 4F 0.75 lb. ai/a A Pendulum AquaCap 1.5 lb. ai/a AB Pendulum 3.0 lb. AquaCap ai/a A 4.5 fl. oz./a Specticle FLO AB Specticle FLO 9 fl. oz./a A
0%
15%
19%
10
Tenacity
1%
23%
29%
11
Tenacity
2
5
5
Table 1. Percent southern crabgrass cover over time.
LSD P = .05
0.25 lb. ai/a AB 0.25 lb. ai/a A
Sept. 24, 2015 Density 1 to 9 190 DAT / 132 DAT2
5
46%
Aug. 20, 2015 Density 1 to 9 155 DAT1 / 97 DAT2
4
1%
June 17, 2015 Density 1 to 9 91 DAT1 / 33 DAT2
3
0.25 lb. Dimension ai/a AB 0.5 lb. Dimension ai/a A 0.38 lb. Barricade 4F ai/a AB Barricade 4F 0.75 lb. ai/a A Pendulum AquaCap 1.5 lb. ai/a AB Pendulum 3.0 lb. AquaCap ai/a A 4.5 fl. oz./a Specticle FLO AB
April 10, 2015 Injury 1 to 9 23 DAT1 / 23 DAT2
2
Untreated
Aug. 20, 2015 155 DAT1 / 97 DAT2
1
Tall fescue
June 17, 2015 91 DAT1 / 33 DAT2
Treatment
Percent Crabgrass Cover
1
6
4
3
1
6
6
7
1
7
5
6
2
7
6
7
1
6
6
6
1
7
6
7
1
5
5
6
4
5
3
5
6
4
2
3
1
7
6
6
1
7
5
6
1
2
1
1
Table 2. Tall fescue injury and density in this study.
28 | Virginia Turfgrass Journal May/June 2016 www.vaturf.org
Tall fescue injury: 1 = no injury, 9 = complete death Tall fescue density: 1 = no stand, 9 = complete turf cover
T
his trial was initiated in an established stand of ‘Southern Belle’ tall fescue. The purpose was to compare split applications to single applications of Dimension, Barricade and Pendulum, common preemergence herbicides used for crabgrass control. The rate used for the single-application treatments was cut in half for each of the split-application treatments, so the total amount of herbicide was the same for