Laboratory evaluation of some environmentally safe chemicals against the two spotted spider mite, Tetranychus urticae and its predator insect, Stethorus gilvifrons

The present study was directed to evaluate the relative toxicity of eight compounds; four pesticides (abamectin, cypermthrin, etoxazole and chlorfluazuron), two mineral oils (Chemesol and Supermasrona) and two plant extracts Worm wood (Chrysanthemum morifolium) and Melia azedarach against adult females of the two spotted spider mites Tetranychus urticae and its predatory insect Stethorus gilvifrons using leaf-disc dip technique. The effects of sublethal doses of these compounds on some biological and behavioral characteristics of this mites and its predator was also examined. The results indicated that, abamectin was the highest toxic compound to the adult females of T. urticae, followed by chlorfluazuron and cypermethrin while etoxazole was the least toxic one. Abamectin still considered the best compound, which has a special effect to adult females of predator S. gilvifrons, followed by chlorfluazuron, and cypermthrin, in addition, etoxazole was the least toxic one. Moreover, chlorfluazuron, cypermethrin and Supermasrona were the most effective compounds on egg deposition of the adult female mites and caused the highest reduction in egg deposition comparable to the control treatment. Etoxazole had the least effect on egg deposition that confers a chance to produce eggs enough for predation including mite egg, the preferable stage, for some predators. Cypermethrin was highly toxic compound that caused the highest decrease in egg hatchability on leaf discs against egg stage of the T. urticae but etoxazole and worm wood extract were the least effective ovicidal action. Abamectin and cypermethrin were the most effective chemicals that caused a decrease in prey egg consumption comparable to the control treatment, while etoxazole had the least effect. Data also indicated that the predators egg deposited under the chemical treatment were less than that deposited under normal conditions (untreated). Cypermethrin was the most effective chemical, which caused a decrease in eggs deposited by adult female predator S. gilvifrons comparable to the controls. Etoxazole and worm wood extract were the safest compounds that allowed the predator's eggs to hatch producing the next stages necessary as biological agent that minimize prey populations.