Chemical control of Eremophilla mitchellii

Abstract

Experiments to test the effectiveness of the butoxyethanol ester of 2,4,5-trichlorophenoxyacetic acid on seedling growth and regrowth from old root-stocks of Eremophila mitchellii Benth. were conducted in two localities in south-western Queensland. The treatments were applied during April, May, July, and October 1963, as both water and diesel distillate based emulsions. Phthalic acid and dimethyl phthalate were added to half of the water and half of the diesel treatments respectively, to determine whether either of these chemicals would enhance the effect of the hormone. At no time of application was any water based treatment effective, but the hormone in diesel distillate was effective at all times of the year. A high percentage kill of E. mitchellii was obtained with 0.5 and 1.0 per cent 2,4,5-T in diesel distillate, except on plants having a basal diameter greater than 3 inches. The addition of dimethyl phthalate to the oil-based sprays gave a quicker initial effect, but did not increase the final percentage kill. Diesel distillate alone and in combination with dimethyl phthalate, killed some of the smaller plants, but was ineffective on the larger timber sprayed. At the higher concentrations of 2,4,5-T in diesel distillate, large plants were killed, provided complete wetting of the base of the stem was achieved.