Factors Influencing Postemergence Activity of Chloramben in Velvetleaf (Abutilon theophrasti)

Abstract

Efficacy of soil and/or foliage applications of the sodium salt of chloramben (3-amino-2,5-dichlorobenzoic acid) was compared, and the influence of growth stage and oil base within adjuvants on chloramben efficacy was evaluated on velvetleaf (Abutilon theophrastiMedic. # ABUTH). In greenhouse experiments, soil applications reduced growth of velvetleaf treated at the six- to seven-leaf stage (15-cm height) more than did foliage applications. Simulated rainfall applied 48 h after chloramben was applied to foliage significantly increased chloramben activity. Chloramben plus an oil concentrate applied at 3.4 kg ae/ha plus 2.3 L/ha reduced fresh and dry weight less as growth stage advanced in both greenhouse and field experiments. Origin of oil present in the oil concentrate did not influence the activity of chloramben plus oil concentrate in either the greenhouse or in the field. Chloramben plus oil concentrate reduced seed capsule (boll) production 70% or more in velvetleaf plants treated at each of three growth stages in one year and reduced capsule production 90, 90, and 28% in plants treated at early vegetative, late vegetative, and flowering stages, respectively, in the second year. Viability of seed was less from plants treated at a vegetative stage compared to the flowering stage.