Research Report
A New Liquid Formulation of Quinclorac for Smooth Crabgrass Control in Cool-Season Turf Virginia Tech Researchers: Sandeep S. Rana, Doctorate Student, and Shawn D. Askew, Ph.D., Associate Professor, Turfgrass Weed Science, Plant Pathology, Physiology and Weed Science Dept. Research Cooperators: Quali-Pro
C
urrently, many herbicides (Balan, Ronstar, Barricade, Dimension and Tupersan) are labeled for preemergence control of smooth crabgrass (Digitaria ischaemum (Schreb.) Schreb. Ex Muhl.) in both warm- and cool-season turf; however, postemergence control options (MSMA/DSMA, dithiopyr, fenoxaprop and quinclorac) for smooth crabgrass are limited. The control options are even more limited since the loss of MSMA in sports turf and restrictions placed for golf and sod production. Presently, quinclorac is among the most effective postemergence herbicides for smooth crabgrass control, but quinclorac has only been offered as a dry formulation throughout its entire patent life. Although dry formulations require “softer” packaging, have less shipping weight and impart less exposure risk to handlers, recent market analyses continue to indicate that liquid formulations of sprayable pesticides are most desirable among turf managers. Recently, a liquid formulation of quinclorac became available by BASF Corporation under the trade name Drive® XLR8. Previously, Quali-Pro had only offered a dry formulation of quinclorac, but it has now developed a liquid formulation of quinclorac (Quali-Pro Quinclorac 1.5 L) that uses new formulation technology, allowing faster dispersion, better cold-water mixing and safer inert materials and surfactants.
Our research
Field trials were initiated on July 25, 2013, on a perennial ryegrass fairway (0.6" height) at the Turfgrass Research Center (TRC) at Virginia Tech in Blacksburg to evaluate smooth crabgrass control efficacy of and perennial ryegrass sensitivity to the liquid formulation of quinclorac [QualiPro Quinclorac 1.5 L (QPQ 1.5 L)] compared to the dry
formulation [Quali-Pro Quinclorac 75 DF (QPQ 75 DF)] and the industry standards, Drive® XLR8 [quinclorac (DXQ 1.5 L)] and Acclaim Extra® [fenoxaprop) (AEF 0.57 EW)]. The herbicide treatments included: • QPQ 75 DF 75 DF at 16 oz. wt./A • QPQ 1.5 L at 64 fl. oz./A • DXQ 1.5 L at 64 fl. oz./A (Drive XLR8) • AEF 0.57 EW at 21.1 fl. oz./A (Acclaim Extra) All herbicide treatments included methylated seed oil (MSO) at 0.25% v/v to simulate conditions of limited absorption, a common problem while using dry formulations of herbicides.
Research results
None of the herbicide treatments injured perennial ryegrass (data not shown). At 7 days after treatment (DAT), QPQ 1.5 L and DXQ 1.5 L controlled smooth crabgrass equivalently at 94% and 95%, respectively, and greater than QPQ 75 DF (77%) and AEF 0.57 EW (68%) (Figure 1a., Figure 2). Lower smooth crabgrass control from QPQ 75 DF is because of lower rate of MSO (0.25% v/v) used in this study. Moreover, smooth crabgrass control from AEF 0.57 EW peaks at 14 DAT. At 14 DAT, QPQ 1.5 L, AEF 0.57 EW and DXQ 1.5 L controlled smooth crabgrass equivalently at 93%, 97% and 95%, respectively, and greater than QPQ 75 DF (63%) (Figure 1b., Figure 2). At 28 DAT, QPQ 1.5 L, AEF 0.57 EW and DXQ 1.5 L continued to provide equivalent higher levels of smooth crabgrass control at 93%, 96% and 92%, respectively; whereas, smooth crabgrass control with QPQ 75 DF decreased even further (47%) (Figure 1c., Figure 2). Researchers at Maryland and New Jersey have also reported quinclorac and fenoxaprop to effectively control smooth crabgrass postemergence, both in warm- and cool-season turf.
20 | Virginia Turfgrass Journal May/June 2014 www.vaturf.org