~ 39 ~ Journal of Entomology and Zoology Studies 2022; 10(5): 39-43 E-ISSN: 2320-7078 P-ISSN: 2349-6800 www.entomoljournal.com JEZS 2022; 10(5): 39-43 © 2022 JEZS Received: 12-06-2022 Accepted: 14-07-2022 Mitch M Legwaila Botswana University of Agriculture and Natural Resources, P/Bag 0027, Gaborone, Botswana Motshwari Obopile Botswana University of Agriculture and Natural Resources, P/Bag 0027, Gaborone, Botswana Bamphitlhi Tiroesele Botswana University of Agriculture and Natural Resources, P/Bag 0027, Gaborone, Botswana Corresponding Author: Mitch M Legwaila Botswana University of Agriculture and Natural Resources, P/Bag 0027, Gaborone, Botswana Efficacy of Abamectin against adult spider mite, Tetranychus cinnabarinus (Acari: Tetranychidae) on tomato in Botswana Mitch M Legwaila, Motshwari Obopile and Bamphitlhi Tiroesele DOI: https://doi.org/10.22271/j.ento.2022.v10.i5a.9052 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. Keywords: Abamectin, efficacy, carmine spider mite, tomato Introduction Tomato (Solanum lycopersicum var. lycopersicum), which belongs to the family Solanaceae, is the most popular and widely consumed vegetable crop grown in open fields, greenhouses and shade houses of the world including Botswana (Badimo 2020; Leungo et al. 2012; Mwandila et al. 2013) [2, 17, 22] . Tomato is highly valued for its economic and nutritional value (Boamah et al. 2010; Dube et al. 2020; Shiberu and Getu 2018) [5, 8, 27] and constitutes an important part of household diet and national economy. However, local farmers often lament the destruction by a wide range of invertebrate pests as a main cause of low production and quality in Botswana. Studies conducted in Botswana have identified several invertebrate pests attacking tomato which include the African bollworm (Helicoverpa armigera), tomato semi-looper (Chrysodeixis acuta), whitefly (Bemisia tabaci), aphids, tomato leaf miner (Tuta absoluta) and spider mites (Tetranychus spp.) (Baliyan 2012; Munthali et al. 2004; Obopile et al. 2008) [4, 21, 24] . One of the most serious pests of tomato in Botswana is the carmine spider mite (Tetranychus cinnabarinus Boisduval, 1867) (CSM). Heavy spider mite infestation causes leaf drop, loss of water and even death of the host plant, leading to severe economic losses (Bu et al. 2015; Jia et al. 2011; Liang et al. 2011) [13, 18] . Among the different control measures available, farmers in Botswana prefer to use chemicals to control pests because they give quick results (Baliyan and Rao 2013; Leungo et al. 2012) [3, 17] . Some farmers spray their crops repeatedly regardless of the presence of pests or damage symptoms. Most of the active ingredients used by farmers are classified either as extremely hazardous or highly hazardous by World Health Organization (WHO 2020) [30] . This has serious implications on the health and safety of farmers. Because of the diversity and abundance of alternative hosts, the disruption of its natural enemies, its high reproductive potential and genetic elasticity spider mites quickly develop resistance to acaricides used against them (Sato et al. 2005) [26] . Abamectin is one of the most commonly used acaricides for the control of spider mites in Botswana (Obopile et al. 2008) [24] . Abamectin is a natural fermentation product of the soil bacterium, Streptomyces avermitilis (Hayes and Laws 1995; Kim and Goodfellow 2002) [10. 14] .