Effects of imazethapyr treated oil palm frond residue mulch on weed control and ornamental plant quality in nurseries

Abstract

A combination of oil palm frond (OPF) mulch and imazethapyr has been shown to provide good weed control in crop plantations, but information on its potential use for weed control in nurseries is limited. This study aims to evaluate the effect of imazethapyr in combination with OPF mulch on the inhibition of goosegrass, slender cyperus, coat buttons and phytotoxicty on ornamental plants under glasshouse conditions. Three suboptimal rates of imazethapyr, representing low, medium and high rates, are applied alone or used to treat 3.5 t ha−1 OPF residue powder (< 2mm). The low rate of imazethapyr at 10 g a.i. ha−1 and the OPF mulch alone inhibit seedling growth of goosegrass, slender cyperus and coat buttons by 40%-60%. The OPF mulch treated with imazethapyr at this rate acts synergistically and provides 80%-95% inhibition ofweed growth. However, increasing the rate of imazethapyr over 10 g a.i. ha−1 does not further improve weed inhibition, and results in antagonism on goosegrass and slender cyperus emergence. A subsequent experiment with the low rate of imazethapyr incorporated with OPF mulch causes moderate phytotoxicity on Chinese aloe and coral swirl, but minimal or no injury was observed for jasmine, cactus, puding and euodia at 4–12 weeks after treatment. Results suggest that incorporation of imazethapyr at 10 g a.i. ha−1 with OPF mulch can effectively control goosegrass, slender cyperus and coat buttons without injuring jasmine, cactus, puding and euodia.