Abstract

Two field experiments were conducted to evaluate the reduction of torpedograss canopy by multiple split applications of quinclorac applied postemergence (POST) to bermudagrass golf course roughs in Florida. In one experiment, quinclorac treatments were reapplied for a second year to the same plots, followed by biomass harvest, to evaluate reduction of torpedograss rhizomes. Quinclorac sprayed at 1.68 kg/ha/yr visually reduced torpedograss canopy to a varying extent, depending on the number of split applications. The most effective treatment, 0.42 kg/ha quinclorac applied four times each year for two years, reduced torpedograss canopy from 10%, compared with 86% torpedograss canopy in untreated plots, and reduced torpedograss dry wt to 1,570 kg/ha, compared with 8,010 kg/ha in untreated plots. Following two years of reapplication with the commercially labeled treatment, quinclorac at 0.84 kg/ha applied twice per year, torpedograss canopy was reduced to 45% and dry wt to 4,640 kg/ha. Visual evaluation of canopy was too optimistic in representing the herbicidal control of torpedograss by quinclorac, as torpedograss regrew from rhizomes, and canopy was a relatively small part of the plant. In plots not chemically treated, pachymorph rhizomes were 63%, leptomorph rhizomes were 24%, and leaves were only 13% of the total dry wt of torpedograss.