Effect of Demeter Adjuvant (Rizospray Extremo) in Enhancing the Effectiveness of Herbicide Mixtures for Effective Weed Control in a Matured Oil Palm Plantation in Western Ghana

Abstract

An Adjuvant is an additive chemical that is known to enhance the effectiveness of pesticides like herbicides by helping to improve the absorption of the herbicides by weeds and may eventually help to reduce the dosage of the herbicides used. In the current trial, the adjuvant (Rizospray Extremo) was applied at 3 rates, i.e., 73 ml/ha, 109 ml/ha and 145 ml/ha. The herbicide mixtures used for the trial were glyphosate (glyphader) and triclopyr (garlon) mixtures at 436 ml/ha and 182 ml/ha respectively (60 mls glyphosate + garlon at 25 mls mixed in 15 litres of water). The herbicide control was glyphosate at 436 ml/ha + garlon at 182 ml/ha (with no adjuvant) whiles one plot was used as the no herbicide control. Weeds on the site include both soft weeds and woodies. Observations on weed mortality were made on weekly basis. Generally, herbicide application (with and without the adjuvant) effectively controlled the soft weeds at the site. Percentage weed growth reduction and herbicide efficacies generally increased with increasing rates of the adjuvant. Highest herbicide efficacy of 96% was obtained by the use of the adjuvant at 145 ml/ha. The treatments differed significantly mostly in their levels of control of the woody weeds at the site with adjuvant application at 145 ml/ha inducing the highest control of woody weeds (herbicide efficacy of 95.7%), whiles Adjuvant application at 73 ml/ha induced an efficacy of 88.91% on the woodies at the site. Glyphosate plus garlon application (without the use of adjuvant) induced an efficacy of 78.39%. The adjuvant was very effective in controlling weeds with waxy cuticles like the Thaumatococcus spp which were not effectively controlled without the use of theand adjuvant. The adjuvant (Rizospray Extremo) is therefore recommended for use in herbicide mixtures for spot spraying of woodies or noxious weeds at the site.