Toxicity, Absorption, Translocation, and Metabolism of Foliar-Applied Chlorimuron in Yellow and Purple Nutsedge (Cyperus esculentusandC. rotundus)

Abstract

Greenhouse and laboratory experiments were conducted to study the activity of foliar-applied chlorimuron in yellow and purple nutsedge. Foliar-applied chlorimuron caused injury to both yellow and purple nutsedge at rates as low as 5 g ai/ha. Visible injury increased as rates increased from 5 to 20 g/ha at all weekly evaluation dates. At 28 days after application, there was 84% control of yellow and 100% control of purple nutsedge from 20 g/ha of chlorimuron. In both species, all rates of chlorimuron reduced shoot dry weight, inhibited secondary shoot production, and inhibited resprouting of parent tubers attached to treated plants. Over 92% of the applied label was recovered, when 15 μl of 3.46 mM14C-chlorimuron solution containing 0.18 μCi was applied to a 1 cm2area in the middle of the fourth fully expanded leaf. Over 12% of the total14C applied was absorbed, with over 15% of that being translocated within 1 day after application in both species. More than 76% of the absorbed14C in yellow nutsedge and 72% in purple nutsedge remained in the treated area. In both species, basipetal transport was limited. Analysis of plant tissue extracts by thin-layer chromatography indicated slow degradation of chlorimuron in both species. Susceptibility of yellow and purple nutsedge to chlorimuron appears to be due to the rapid absorption and translocation rates in relationship to the slow degradation rate of the active parent compound.