Toxicological and Biological Responses of Tetranychus urticae Koch to Three Pesticides and their Side Effect on the Predatory Mite, Euseius scutalis (A.-H.)

Cucumber Cucumis sativus L. is one of the most popular vegetables in Egypt. Unfortunately, it is a target for several insect, mite pests and pathogens, which mainly controlled by using chemical pesticides. The effect of a single application of the recommended concentration of the acaricide, hexythiazox (10% EC), the insecticide, acetamiprid (20% SP) and the fungicide, ridomil gold plus (71.5% WP) against the main mite pest, Tetranychus urticae Koch was evaluated in a greenhouse. Acetamiprid was the most toxic compound to T. urticae causing an initial kill of 31.12%, residual efficiency of 69.90% and total effect of 50.51%. These values decreased for hexythiazox to 21.17, 65.26 and 43.21%, while they were 17.55, 26.46 and 22.0% when cucumber treated with ridomil gold plus, respectively. The initial, residual and total effects of the aforementioned compounds on the predatory mite, Euseius scutalis (Athias-Henriot), as a non-target mite, were lower and averaged 23.23, 22.30 and 22.76%; 39.04, 41.68 and 40.36%; and 13.64, 11.79 and 12.71%, respectively. Half of the recommended concentration was applied in laboratory to determine the side effect of these compounds on the life-table parameters of the non-target predatory mite, E. scutalis to have information about the forthcoming offspring as compared with the mite pest T. urticae. Tested pesticides generally prolonged mean generation time T, doubling time DT, while reduced the net reproductive rate R_o, natural increase r_m and finite increase e^rm. The adverse effect of chemical application was noticeably greater on mite pest T. urticae than predatory mite E. scutalis.