Phytotoxic Activity of Geraniol-Treated Lemongrass Leaf Mulch against Common Weeds in Nurseries

Hand weeding continues to be one of the most laborious aspects of nursery maintenance. Oxygenated monoterpene, an important group of secondary metabolite found in essential oils, has a potential herbicidal activity that could be exploited as natural herbicide whereas organic mulch could delay weed emergence. Thus, this study aimed to examine the phytotoxicity of geraniol, an oxygenated monoterpene compound, in combination with lemongrass leaf mulch against three common weeds, Eleusine indica (grass), Cyperus distans (sedge), and Tridax procumbens (broadleaf). Greenhouse experiments were carried out by treating 4.0 t/ha lemongrass leaf mulch with 7.5% (v/v) geraniol compound. The pretreated mulch acted synergistically and inhibited the emergence and shoot growth of T. procumbens completely. However, the pretreated mulch exhibited a moderate inhibitory effect on C. distans emergence and growth. Geraniol-treated lemongrass leaf mulch acted synergistically and inhibited the emergence of E. indica by 72%, but it acted antagonistically and caused a 45% reduction of shoot biomass. The present findings suggest that geraniol-treated lemongrass leaf mulch has potent herbicidal activity but its phytotoxic effect is species-dependent.