Abstract
Velvet mesquite, locally known as al-ghaf bahri (Prosopis juliflora), is a well-known invasive alien plant species in several regions around the world, including Oman, with various environmental effects. The allelopathic effect of P. juliflora leaves and seed pods on native ghaf (P. cineraria) and a crop species, mung bean (Vigna radiata) was demonstrated. Results indicated that P. juliflora extracts have inhibitory effects on seed germination and seedling growth of both species, particularly on P. cineraria when exposed to pod extracts. For eradication experiments, three herbicides (tribenuron methyl, clethodim and 2,4-D & MCPA) were investigated to determine their inhibitory properties on seed germination, and on the growth and development of young seedlings of P. juliflora. Generally, germination time (GT50, time required for 50% of seeds to germinate) and germination percentage (%) indicated that only 2,4-D & MCPA treatment showed a significant effect on inhibiting seed germination and stopping seedling growth relative to the other two herbicides. The effect of 2,4-D & MCPA was supported by significant reduction in above-ground fresh biomass. The data clearly illustrate the potential negative effects of P. juliflora on other plant species and its tolerance of herbicide treatment. On a farm scale, limited application of 2,4-D & MCPA on young P. juliflora seedlings would be recommended as an effective way to limit further spread and distribution and consequently to successfully eliminate this invasive alien plant.