Competition from Vulpia myuros (L.) C.C. Gmelin in pastures, and its control by coating seeds with herbicides

Abstract

Competition from the annual grass weed rat's tail fescue (Vulpia myuros [L.] C. C. Gmelin) seriously reduces the establishment of autumn sown, direct-drilled pastures on the Northern Tablelands of New South Wales. Field populations of rat's tail fescue of 43 000 seedlings m-2 have been observed. The effect of a range of rat's tail fescue populations (0, 5, 10,20,40 and 80x 103 seeds m-2) on the early growth of lucerne and phalaris was measured in a glasshouse experiment in soil amended with either high or low levels of nitrogen and phosphorus. Under both fertility regimes, competition from rat's tail fescue was severe at densities of 5x 103 seeds m-2 and above with leaf number, plant height and DM yield of the sown species being markedly reduced in the presence of rat's tail fescue. In 2 further glasshouse experiments with lucerne, a wide range of seed-applied herbicides (EPTC, benfluralin, napropamide, chlorthal-dimethyl, trifluralin, oryzalin, alachlor, diclofop-methyl and 2,2-DPA) were evaluated at several rates to control germinating rat's tail fescue. EPTC significantly reduced weed density at rates as low as 0.35 kg ha-1 and was the only herbicide to significantly reduce the yield of rat's tail fescue (at rates as low as 0.1 kg ha-1) and to allow an increase in the yield of the sown lucerne. Confirmation of the effectiveness of seed-applied EPTC under direct-drill conditions is still needed.