Evaluation of pre-emergence herbicides on four proteaceous species.
Field trials were conducted at Kula, on the Hawaiian island of Maui, to evaluate the use of pre-em. herbicides and 2 synthetic mulches for weed control in Leucadendron hybrid cv. Safari Sunset, Leucospermum cordifolium cv. Pincushion, Banksia menziesii cv. Pink Frost Banksia and Protea neriifolia cv. Pink Mist. Oxadiazon at 4.5 kg/ha, oryzalin alone at 2.2-6.7 kg (1%) or in combination at 1% with 2% oxyfluorfen in granular mixtures at 3.4-10.1 kg, were applied to seedlings or 1-year-old root cuttings on 18 Apr. 1986 and at 3 month intervals thereafter for 2 years. The mulches comprised a black polypropylene woven ground cover (BPWGC) and a polyester geotextile fabric (PGF). All treatments resulted in >70% control of Pennisetum clandestinum, Sonchus oleraceus, Ricinus communis, Trifolium repens and Oenothera laciniata by 267 d after sowing (DAS), the best (93-100%) being by the use of the BPWGC. Both mulches also resulted in 95-100% control of Medicago truncatula, compared to only 53-78% by the herbicides. All treatments increased trunk diam. of B. menziesii, Leucadendron and L. cordifolium, from control increments of 5-9 mm by 357 DAS to 15-38 mm. Most treatments also enhanced trunk growth of P. neriifolia above the control value of 18 mm to 23-33 mm, but the highest concn of oryzalin ± oxyfluorfen was inhibitory.