Evaluation of leaf extract of Eucalyptus globulus L. against Tetranychus urticae Koch, pest ofokra

摘要

Aqueous leaf extract of Eucalyptus globulus L. was bioassayed by two methods against Tetranychus urticae Koch, a major pest of okra (Abelmoschus esculentus L.). In both the bioassay methods (direct spray and treated food), the mites exhibited mortality in a concentration dependent manner, however, all the concentrations were significantly better than control. Highest concentration (10%) caused maximum mortality (81 to 93%) of various developmental stages of T. urticae than the lowest concentration (0.37%) with 36 to 59 percent mortality. Direct spray technique proved to be a better method due to lower LC_(50) and LT_(50) values than treated food bioassay. In direct spray method, LC_(50) values were 0.18, 0.39, 0.44 and 0.98 per cent with LT_(50) values as l.ld, 3.1h, 3.7h and 5.8h, for egg, larva, nymph and adult, respectively.