Field Efficacy of Selected Chemical Pesticides against two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranchidae), on Tomato in the Central Rift Valley of Ethiopia

The two-spotted spider mite (Tetranychus urticae) is a significant pest affecting tomato production in Ethiopia, leading to substantial yield losses and economic challenges for farmers. This study evaluated the efficacy of seven widely used chemical pesticides compared to an untreated control for controlling T. urticae infestations and their impacts on tomatoes. Field experiments were conducted during the 2021 and 2022 cropping seasons at Melkassa Agricultural Research Center using a randomized complete block design with three replications. Pesticides were applied at recommended rates, and reductions in mite populations (egg, nymph, adult) on eight treatments were evaluated using the percentage reduction over control (PROC), and mean separations with ANOVA on yield were done. Results revealed that Cyenopyrafen and Abamectin were the most effective treatments, achieving PROC values of 63.2% and 60.1%, respectively, in 2021, with corresponding marketable yield outputs of 16.5 and 15.45 tons/ha. However, efficacy declined across all treatments in the 2022 tomato production season, although Cyenopyrafen and Abamectin maintained their superior performance compared to other treatments. Other treatments, such as Abamectin-emamectin benzoate, exhibited limited effectiveness, with PROC values below 20%. The partial economic analysis highlighted Cyenopyrafen and Abamectin as the most cost-effective options, generating net profits of USD 10,068/ha and USD 9,395/ha, respectively, with high benefit-cost ratios (BCR) of 3.75 and 3.45. These findings underscore the importance of selecting effective pesticides to maximize tomato yields and economic returns. For sustainable production, integrating these chemical controls into an integrated pest management (IPM) strategy is essential. Future studies should focus on resistance monitoring, optimizing application schedules, and assessing environmental impacts on non-target organisms to ensure sustainability in tomato production in Ethiopia.