Evaluation of metsulfuron-methyl and combinations in controlling weeds in juvenile oil palm plantation

Abstract Herbicide mixtures provide good control at considerably lower dosages than dosages utilized in single applications. A study was conducted at the Benso Oil Palm Plantation to evaluate the efficacy of application of sole Metsulfuron-Methyl (a residual sulfonylurea herbicide) and its combinations with Glisat (glyphosate) in controlling weeds under two-year old oil palm. The sole Metsulfuron-Methyl application rates were a) 190.5g/ha; b) 381g/ha, c) 571.4g/ha or in combination with Glisat at rates d) Metsulfuron-Methyl at 190.5g/ha + Glisat at 2.8 l/ha, e) Metsulfuron-Methyl at 190.5g/ha + Glisat at 4.3 l/ha and Metsulfuron-Methyl at 381g/ha + Glisat at 2.8 l/ha; Metsulfuron-Methyl at 381g/ha + Glisat at 4.3 l/ha. No chemical treatment (water) and Ceresate at 1.5 L/ha served as the control treatments. Application of sole Metsulfuron-Methyl or in combination with Glisat significantly reduced weed dry weight. The reduction in weed weight was more pronounced at 4 weeks after treatment. The sole Metsulfuron-Methyl application was less effective in controlling weeds than Ceresate or Metsulfuron-Methyl and Glisat combinations. Herbicide efficacy recorded for Metsulfuron-Methyl sole at different rates at 4 WAT ranged from 64 to 75% for broadleaves and 35 to 40% for grasses. The combined application of Metsulfuron-Methyl and Glisat was effective in controlling both broadleaves and grasses. Metsulfuron-Methyl sole or in combination with Glisat had no adverse effect on oil palm growth and significantly improved vegetative parameters. A combined application of Metsulfuron-Methyl at 190.5 g/ha and Glisat 2.8 L./ha is recommended in controlling both broadleaves and grasses under oil palm plantations.