Sequential DCPA Treatments for Weed Control in Turfgrasses1

Abstract

AbstractIn the southeastern USA, herbicides have not generally given consistent preemergence control of large crabgrass [Digitaria sanguinalis (L.) Scop.] and annual bluegrass (Poa annua L.). DCPA (dimethyl tetrachloroterephthalate) was applied as single and repeated treatments over a 3‐year period for large crabgrass control at Griffin and Blairsville, Georgia, and for annual bluegrass control at Griffin. The soil types were Cecil sandy loam (Typic Hapludult) or sandy clay loam at Griffin and Hatboro loam (Typic Fluvaquents) or sandy loam at Blairsville.None of the DCPA treatments controlled large crabgrass or annual bluegrass consistently at the, rates included in these studies. Treating plots with DCPA at 11.2 kg/ha in both March and June gave the greatest control in 2 of 3 years at each location. A significant multiple correlation between temperature prior to treatment and weed control ratings indicated that poor control of large crabgrass was related to germination of crabgrass prior to treatment. High temperatures that induced germination of crabgrass during 2 weeks prior to time of treatment resulted in less control than in years with lower temperatures. This emphasizes the need for early application of DCPA in Georgia.