Responses of five plant species sprayed with sublethal doses of metsulfuron methyl

Two wetland plant species, Mimulus ringens (Monkey-flower) and Bidens cernu a (Bur-marigold), two terrestrial species, Sinapis arvensis (Wild mustard) and Phaseolus vulgaris (Beans), and one species found in both wet and dry h abitats, Echinochloa crus-galli (Barnyardgrass), were exposed to 1%(0.045 g -ai/ha) and 10% (0.45 g-ai/ha) of recommended label rate of the sulfonylure a metsulfuron methyl. The objective of the study was to investigate the eff ect of sublethal doses of metsulfuron methyl. Chemical analyses of herbicid e residues showed that, in many cases, less than the intended doses reached the plants. Nevertheless all species exhibited marked effects on the veget ative and reproductive growth when sprayed at 10% label rate, and to a less er extent at 1% label rate. Seed weight was significantly reduced for B, ce rnua and S. arvensis. The importance of the various strategies developed by the five species is discussed.