Interval between sequential applications of asulam for regrowth control of torpedograss (Panicum repens L.)

Abstract

Two field experiments each conducted during a 1 year period at the Agricultural Experiment Farm, University of the Ryukyus, Japan evaluated the interval needed between sequential applications of asulam (3 kg ai ha−1) for successful control of torpedograss (Panicum repens L.). Regrowth of torpedograss from rhizomes was lowest when asulam was applied at 40‐day intervals. Application at intervals of 70 days or longer completely controlled above‐ground shoots but not regrowth from rhizomes. Above‐ground biomass of torpedograss regrowth was 7‐ and 49‐fold higher when asulam was applied at 70 and 100 day intervals, respectively, compared with 40‐day intervals. Asulam applied three times at 40‐day intervals starting 40 days after land preparation provided almost total torpedograss control 1 year after the initial application.