| Abstract/Contents: | "Fenoxaprop effectively controls crabgrass (Digitaria spp.) in tall fescue [Festuca arundinacea Shreb.] turf. Antagonism with growth regulating herbicides reduces potential to apply fenaxoprop in combination with many products for broadleaf weed control. Fluroxypyr is a pyridinoxy acid, broadleaf herbicide which may have potential for use in mixtures with fenoxaprop. Field experiments investigated fenoxaprop efficacy for smooth crabgrass (Digitaria ischaemum) control when applied alone and in combination with either fluroxypyr or a pre-packaged mixture of 2,4-D, dicamba , and mecoprop (MCPP) in tall fescue. Experiments were conducted on mature stands of tall fescue from June to August 2009 at the University of Georgia in Griffin, GA and the University of Tennessee in Knoxville, TN. Soil in Georgia was a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludults) with 4.6% organic matter and a pH of 5.6. Soil in Tennessee was Sequatchie loam soil (fine-loamy, siliceous, semiactive, thermic humic Hapludult), measuring 6.2 in soil pH and 2.1% in organic matter content. The tall fescue cultivar at each location was unknown. Irrigation at each location was applied to prevent wilt and both sites were mowed weekly at 6.4 cm height with clippings returned. Smooth crabgrass and white clover ground cover averaged 21% and 23%, respectively, on the day of initial treatments in Georgia, and 50% and 15%, respectively, in Tennessee. Experimental design was a randomized complete block with four replications. Fenoxaprop (Acclaim Extra 0.57SC, Bayer Crop Science, Montvale, NJ 07645) was applied at 25, 50, 100, 200, or 400 g a.i./ha (0.36, 0.72, 1.43, 2.86, or 5.7 oz a.i./acre) alone, in combination with fluroxypyr (Spotlight 1.5L, Dow AgroSciences, Indianapolis, IN 46268) at 0.53 kg a.i./ha (0.47 lb a.i./acre), and in combination with a pre-packaged mixture of 2,4-D + dicamba + MCPP (hereafter delineated as three-way mixture). This three-way mixture was a prepackaged formulated product (Trimec Classic® 2.72 SL, PBI Gordon Corp., Kansas City, MO 64101) containing 237, 64, and 25 g/L (1.98, 0.53, and 0.21 lb/gal) of 2,4-D, dicamba, and MCPP, respectively; it was applied in combination with each rate of fenoxaprop at 4.7 L/ha (4 pt/acre) or 1.1, 0.29, and 0.12 kg a.i./ha, respectively (1, 0.26, and 0.11 lb a.i./acre). An untreated control was included in each block. Treatments were applied on June, 10 2009 in Georgia and June 3, 2009 in Tennessee. In Georgia, treatments were applied to 1 x 4.5-m (3 x 15-ft) plots by making two passes in opposite directions with a single nozzle CO2 pressured sprayer calibrated to deliver a total 375 L/ha (40 gal/acre). In Tennessee, treatments were applied to 1.5 x 3-m (5 x 10-ft) with a CO2 pressured sprayer containing four flat-fan nozzles calibrated to deliver 280 L/ha (30 gal/acre). Sprayers in Georgia and Tennessee had 9504E and 8002 flat-fan nozzles, respectively (Tee Jet, Spraying Systems Co., Roswell, GA 30075). Tall fescue injury was visually evaluated 2, 4, and 8 weeks after treatment (WAT) on a percent scale where 0 equaled no injury and 100 equaled dead turf. Smooth crabgrass control was also assessed visually on a percent scale, where 0 equaled no control and 100 equaled complete control (relative to the untreated control), at 2, 4, and 8 WAT. Data were subjected to analysis of variance at the 0.05 probability level with fenoxaprop, broadleaf herbicide, and location as variables. Treatment by location interactions were not detected, and thus, results were pooled over locations. Smooth crabgrass control from mixtures of fenoxaprop and fluroxypyr was similar to fenoxaprop alone. Smooth crabgrass control with mixtures of fenoxaprop with 2,4-D, plus dicamba, plus MCPP was nearly 50% less than fenoxaprop alone. White clover was completely controlled from mixtures of fenoxaprop and fluroxypyr which was similar to fenoxaprop applied with 2,4-D plus dicamba plus MCPP. Tall fescue injury was not detected on any rating date. Results suggest tank-mixtures of fenoxaprop and fluroxypyr could provide effective control of smooth crabgrass and white clover in tall fescue." |
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