Effect of Chlorsulfuron on the Movement and Fate of Diclofop in Italian Ryegrass (Lolium multiflorum) and Wheat (Triticum aestivum)

Abstract

The basis for chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] caronyl] benzenesulfonamide} antagonism of diclofop {(±)-2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} was investigated in Italian ryegrass [Lolium multiflorum(Lam.) # LOLMU] and wheat (Triticum aestivumL. ‘McNair 1813′). Chlorsulfuron did not affect the chemical stability or volatility of diclofop in spray mixtures over the time and concentration ranges evaluated. Addition of chlorsulfuron (0.11 μg/μl) to a diclofop (2.0 μg/μl) foliar-applied spotting solution did not affect the absorption, translocation, or metabolism of diclofop in 17-day-old Italian ryegrass or wheat. Italian ryegrass and wheat responded differentially to diclofop alone. At 72 h after treatment, 69 and 40% of labeled diclofop penetrated into Italian ryegrass and wheat leaves, respectively. Although little movement of labeled diclofop occurred in either species, more translocated from the treated zone of Italian ryegrass. At 72 h after treatment, the percentages of14C recovered as parent methyl ester, diclofop (free acid), and conjugates in treated leaf extracts were 9, 62, and 25%, respectively, for Italian ryegrass, and 50, 20, and 29%, respectively, for wheat. Differential penetration and metabolism of diclofop are the probable bases for selectivity between wheat and Italian ryegrass. The antagonism of diclofop caused by chlorsulfuron does not appear to be due to an alteration of the molecular fate of diclofop in Italian ryegrass.