the toxicity of acetamiprid, dicholorvos and azadirachtin pesticides on melon aphid, aphis gossypii glover and lysiphlebus fabarum marshall

cotton aphid, aphis frangulae gossypii glover, is a major pest of cucumber in iran. one of the important parasitoids playing role in population control of this pest in the fields and greenhouses is lysiphlebus fabarum marshall. in this study, we investigated sensitivity of different instars of cotton aphids and pupal stage of l. fabarum to field recommended and half-recommended concentration of three pesticides, acetamiprid, dichlorvos and azadirachtin by leaf dipping method. the persistence toxicity test and bioassays were also carried out on adult of parasitoid. results revealed a significant reduction in the toxicity by increasing the nymphal stages of the aphid. these results also demonstrated the highest mortality for dichlorvos on pupal stage ofparasitoid. according to obtained results, lc50 of acetamiprid was 28.18, for dichlorvos was 7.052 and for azadirachtin was 1780.338, µg/lit on adult of parasitoid respectively. based on iobc categories, azadirachtin with stability of less than 5days, dichlorvos with stability 5-15 days and acetamiprid with stability between 15-31 days were classified as short lived (class a), slightly persistent (class b) and moderately persistent (class c), respectively. these results approved a better integration potential of azadirachtin with the parasitoid, l. fabarum, for aphid control.