author(s)
Mitch M Legwaila, Motshwari Obopile and Bamphitlhi Tiroesele

abstract
The efficacy of abamectin against the carmine spider mite (CSM) on tomato was studied in the laboratory at Botswana University of Agriculture and Natural Resources, Gaborone, Botswana. The acaricide was applied at five dosages including the recommended label rate. Each treatment was replicated three times. The results were analysed using probit analysis where LD₅₀ and LD₉₀ values found with the acaricide were estimated at different assessment periods (24, 48, 72 and 96 hours) following application and used to determine effectiveness of the acaricide. When the treatments were assessed at 24, 48, 72 and 96 h, LD₉₀ values against spider mites were 0.82, 0.71, 0.69 and 0.64. This indicated that abamectin was highly effective against spider mites. The slopes of the probit lines assessed at 24, 48, 72 and 96 h after application were 6.68, 6.97, 6.62 and 4.46. This indicates a rapid change in mortality with increase in acaricide dosage. The study shows that abamectin can be a valuable component of integrated spider mite control programme under Botswana conditions. Further research and field testing is necessary to confirm these laboratory findings.