Residual effect of imidacloprid and pymetrozine on orientation behaviour of Lysiphlebus fabarum Marshall, a parasitoid of the black bean aphid Aphis fabae Scopoli.

For suitable insecticides selection in integrated broad bean aphid management, testing their side-effects on Lysiphlebus fabarum Marshall is needed. Therefore in this research, sublethal effect of imidacloprid and pymetrozine were investigated on orientation behavior of sexual population of L. fabarum using olfactometer device. Mated females (< 48h old) were exposed to concentrations of 1.1 and 646.5 mg a.i./l (LC25) of imidacloprid and pymetrozine, respectively. Results of the olfactory responses demonstrated that the parasitoid wasps had a significant preference to volatiles of leaves contained aphids and their honeydew in imidacloprid, pymetrozine and control treatments (P < 0.05) compared to leaves without them. Responses of the parasitoids to volatiles of leaves contained aphids and honeydew vs leaves contained aphids and without honeydew and to volatiles of leaves contained honeydew vs leaves without aphids and their honeydew showed that parasitoids exposed to imidacloprid had no significant preference to treatments (P > 0.05) compared to pymetrozine and control tratments, they were significantly attracted to volatiles of leaves contained aphids and honeydew and leaves contained honeydew (P < 0.05). In insecticides and control treatments, the repellent effect of leaves and contained aphids treated with imidacloprid was demonstrated against aphid parasitoids. However, pymetrozine did not have such an effect. Therefore application of pymetrozine for parasitoid conservation is recommended.