Acute toxicity and sublethal effects of diazinon on adult stage of Habrobracon hebetor (Hym.: Braconidae)

Habrobracon hebetor Say is an important ectoparasitoid of various lepidopterous larvae. In this study, lethal and sublethal effects of diazinon were evaluated on H. hebetor under laboratory conditions. The adults were exposed to fresh residue of the insecticide applied on glass plates at 26 ± 1^oC, 60 ± 5% RH and a photoperiod of 16:8(L: D) h. Based on the dose-response study, the LC₅₀ value of diazinon was 6.38 µgr a.i. ml^-1. In order to assess the sublethal effects of the insecticides, adult wasps were exposed to an LC₃₀ of the insecticide and then the demographic parameters of live wasps were studied. The results showed that LC₃₀ concentration of diazinon negatively affected the stable population and biological parameters (e.g., r_m, λ, DT, T, eggs laid, hatch rate). The sex ratio of H. hebetor offspring was not significantly affected by the insecticide treatment. The results indicated that diazinon has negative effects on demographic parameters of the parasitoid and semi-field and field tests seem to be necessary.