Selectivity of Bromoxynil in a Resistant and a Susceptible Species

Abstract

The selectivity of 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) in winter wheat (Triticum aestivum L., var. Nugaines), a resistant species, and coast fiddleneck (Amsinckia intermedia Fisch. & Mey.), a susceptible species, was concluded to be the result of a complex of interactions. Wheat was 109 times more tolerant of bromoxynil than was coast fiddleneck. More spray solution was retained by coast fiddleneck plants than by wheat. Bromoxynil penetrated more rapidly into leaves of coast fiddleneck than of wheat. However, these factors did not fully explain bromoxynil selectivity. When differential spray retention and bromoxynil penetration was accounted for, it was estimated that coast fiddleneck was 30 times more susceptible than wheat.