Efficacy, Site of Uptake, and Retention of Bromoxynil in Common Lambsquarters with Conventional and Sprinkler Application

Bromoxynil efficacy, uptake, translocation, and spray retention were investigated when bromoxynil was applied in conventional water volumes of 234 L ha−1and in simulated sprinkler irrigation at 127 000 L ha−1to common lambsquarters. Bromoxynil controlled common lambsquarters similarly regardless of water volume, whereas injury to spearmint, a tolerant crop, was greatest using low water volume. Spray retention was 18 and 38 times greater on common lambsquarters and spearmint, respectively, when bromoxynil was applied in 234 L ha−1than 127 000 L ha−1. Two weeks after applying bromoxynil in 127 000 L ha−1water volume, common lambsquarters dry weight was 60% of the nontreated check where only soil was treated but was 5% of the nontreated check where only leaves were treated. Roots of lambsquarters absorbed 22% of14C-bromoxynil applied to hydroponic solution by 7 d, but only 2% was translocated to the shoots. Percent absorption and translocation of foliar-applied14C-bromoxynil were 15 and 6% greater, respectively, from 0.0096 g L−1than from a 1.2 g L−1bromoxynil solution by 24 h after application. Uptake of bromoxynil was 13% greater through lower than upper leaf surfaces. These results suggest efficacy of bromoxynil applied in large spray volumes is, in part, due to root uptake, efficient foliar uptake and translocation, and uptake from lower leaf surfaces.