Effects of herbicides on wallaby grass (Danthonia spp.) 1. Establishment

Abstract

Two experiments were conducted at Tamworth, New South Wales, to assess the effects of herbicides applied post-sowing pre-emergence, and at 2 post-emergence growth stages, on Danthonia (wallaby grass) dry matter yield, plant number, and plant phytotoxicity. Phytotoxicity was scored visually on a 0-5 scale (0, no phytotoxicity; 5, 100% phytotoxicity). In the post-sowing pre-emergence study, no Danthonia plants survived on plots sprayed with metribuzin (375 g a.i./ha), chlorsulfuron (45 g a.i./ha), or simazine (750 and 1500 g a.i./ha). Phytotoxicity was also high at lower rates of metribuzin (187.5 g a.i./ha) and chlorsulfuron (22.5 g a.i./ha). Dry matter yields and plant numbers on 2,4-D amine and ester treatments were not significantly different from those of unsprayed controls. On metsulfuron-methyl (3 and 6 g a.i./ha) and triasulfuron (21.4 g a.i./ha) treatments, plant numbers were similar to the controls, but Danthonia yields were lower (P<0.05). In seedling stands, the only herbicide that reduced (P<0.05) Danthonia dry matter yield compared with the unsprayed control plots was metsulfuron-methyl applied at 6, 12, and 18 g a.i./ha at the 2-4 tiller stage, and at 12 and 18 g a.i./ha at early stem elongation. At both times of application, Danthonia plant numbers were lowest (P<0.05) on the metsulfuron-methyl 12 and 18 g a.i./ha treatments. Phytotoxicity scores were >2 and highest (P<0.05) on all metsulfuron-methyl plots. These studies indicated that a range of chemicals could be used to control broadleaf weed seedlings, without damaging Danthonia seedlings.