Investigation of a chlorsulfuron-resistant chickweed [Stellaria media (L.) Vill.] population

Abstract

A chickweed population (R) from a farm near Stony Plain, Alberta, was more resistant to chlorsulfuron than a population (S) collected near Vegreville, Alberta. In greenhouse experiments, the S population was controlled completely by chlorsulfuron applied at 5 g ha−1, whereas 22 g ha−1 was required to reduce dry weight of the R population by 50%. Experiments conducted in a germinator indicated that percentage germination of the R population was higher than that of the S population up to ~ 60 h. Growth analyses in the greenhouse indicated that leaf number, leaf area, shoot dry weight, days to flowering, flower number, seed weight and relative yields differed little between the two populations. In field experiments, control of the R population was poor with the sulfonylurea herbicides, chlorsulfuron, metsulfuron methyl, triasulfuron, amidosulfuron and thifensulfuron. Good to excellent control was obtained with cyanazine/MCPA, linuron, metribuzin, mecoprop, bentazon, metribuzin + MCPA, linuron + MCPA, and mecoprop + bentazon. Key words: Sulfonylurea herbicides, chlorsulfuron, herbicide resistance, relative competitiveness