Sublethal effects of imidacloprid and pirimicarb on orientation behaviour of Aphidius matricariae Haliday (Hym.: Braconidae).

Imidacolprid and pirimicarb are conventionally used insecticides for controlling melon aphid, Aphis gossypii Glover  in fields and glasshouses in Iran. Aphidius matricariae Haliday is one of the most impotant parasitoid wasps of A. gossypii. The sublethal effects of mentioned insecticides were investigated on orientation behaviour using olfactometer device. The mortality data were subjected to probit analysis for lethal concentrations calculations and confidence limits. Concentrations of 0.3 and 4.2 ppm (LC₂₅) of imidacloprid and pirimicarb, respectively, were used for olfactometer tests. Adult females were exposed to dry residues on glass tubes for 24 h. Three day old survived wasps were used for orientation tests. Results showed that imidacloprid and pirimicarb had no effects on orientation behaviour of female wasps to the odour of cucumber leaves that were infected by melon aphid although orientation response of female parasitoids toward contaminated leaves to honeydew of aphids was affected by exposure to LC₂₅ of two insecticides. But in all of the tests, access times to treatments by parasitoid wasps exposed to imidacloprid significantly exceeded control.