Efficacy of Biopesticides on Egg Hatchability and Adult Mortality of Tetranychus macfarlanei Baker and Pritchard

Red spider mite Tetranychus macfarlanei Baker and Pritchard (Acari: Tetranychidae) poses a serious threat to successful crop production across Bangladesh. Farmers predominantly rely on chemical pesticides; however, the rapid development of resistance after repeated applications reduces their effectiveness. The aim of this laboratory study was to evaluate the efficacy of selected biopesticides as ecofriendly alternatives for managing T. macfarlanei. Four biopesticides- Celastrus angulatus 1% EW (Bio-Chamak), D-limonene 5% ML (Bio-Clean), Martin 0.5% AS (Biotrin), and Matrin (0.5%) + plant oil (K-mite) - were tested against eggs and adult females of T. macfarlanei. Female mortality was recorded at 12 hr intervals for 18 days, and egg hatchability was assessed 10 days post-treatment. The lethal concentration (LC50) values for adult females were calculated to determine relative toxicity. Results indicated that D-limonene 5% ML and C. angulatus 1% EW exhibited moderate ovicidal activity, while Martin 0.5% AS and Matrin (0.5%) + plant oil had minimal effects on egg hatchability. In contrast, Matrin (0.5%) + plant oil and Martin 0.5% AS showed strong adulticidal effects, with LC50 values of 0.16 ppm and 0.21 ppm, respectively, compared to 6.16 ppm for D-limonene 5% ML and 75.82 ppm for C. angulatus 1% EW. These findings suggest that Matrin (0.5%) + plant oil and Martin 0.5% AS are the most potent formulations against adult T. macfarlanei. In conclusion, these biopesticides, particularly Matrin (0.5%) + plant oil, could serve as promising alternatives to chemical acaricides for the sustainable management of T. macfarlanei and should be further validated in field conditions for integration into future Integrated Pest Management (IPM) programs.