Relative Toxicity of Parathion and Kelthane to the Predacious Mite Phytoseiulus persimilis Athias-Henriot and its Prey, Tetranychus urticae Koch, (Acarina: Phytoseiidae, Tetranychidae) in the Laboratory

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Abstract
The relative toxicity of Kelthane (1,1-bis (p-chlorophenyl) -2,2,2-trichloroethanol), and parathion to Phytoseiulus persimilis Athias-Henriot and its prey, Tetranychus urticae K. (= telarius (L.)), was determined using a Potter Spray Tower. Parathion was found to be far more toxic to P. persimilis than was Kelthane. The LD50 values for Kelthane were 0.051% and 0.29% for T. urticae and P. persimilis respectively, and for parathion were 0.050% and 0.0044% respectively. The LD95 values bore a similar relationship to each other. The two materials were equally toxic to T. urticae. Therefore, use of Kelthane rather than parathion in an environment where P. persimilis and T. urticae were interacting would favour the beneficial species. The statistical aspects of the test method are discussed.