The herbicidal efficacy, persistence, and mobility of fluridone

Abstract

Fluridone (1-methyl-3-phenyl-5((3-trifluoromethyl)-phenyl)-4(lH)-pyridinone) applied in the spring at 0.45 kg/ha or more effectively controlled the annual grasses and broadleaf weeds present in cotton on two soil types. Yellow nutsedge (Cyperus esculentus L.) was controlled by rates of 0.90 kg/ha. Incorporation of fluridone increased its activity and persistence in a Lufkin fine sandy loam but not in Miller clay. Fall applications of fluridone to Miller clay resulted in weed control and cotton (Gossypium hirsutum L.) yields which were not significantly different from spring treatments. Fall applications on Lufkin fine sandy loam did not result in adequate weed control the following spring except where 0.90 kg/ha was incorporated at application. Grain sorghum (Sorghum bicolor L. Moench) planted 1 year after fluridone treatment on Lufkin fine sandy loam was severely injured. Injury to grain sorghum from fluridone applications made the previous year was not noted on Miller clay. Fluridone was satisfactorily extracted from soils with acetonitrile and detected with an electron-capture gas chromatograph. Recovery varied with soil type and ranged from 60 to 101%. The percentage recovery was substantially lowered in most soils when soil moisture exceeded field capacity. In Miller clay a bioassay was limited to detection of fluridone at concentration ranges of 0.05 to 0.45 ppmw when using grain sorghum. No differences in chlorophyll content could be detected at concentrations outside this range..