Sublethal effects of an azadirachtin-based botanical insecticide (commercial product NeemAzal-T/S) on behaviour, life history traits and population growth of one commercial (Dutch strain, D) and two Serbian populations (Bujanovac, B; Negotin, N) of Encarsia formosa Gahan were evaluated in laboratory bioassays. In a two-choice test, parasitoids from all tested populations preferred to parasitise the untreated whitefly nymphs over those treated with 50, 25, 12.5, 6.25 and 3.12 mg/l of azadirachtin. All concentrations caused significant deterrent effects after 24 h, and the following deterrence indices were calculated: 9.7–60.9% (B), 5.5–57.5% (N) and 12.9–63.5% (D). The longevity of adults exposed for 48 h to residues of the botanical insecticide (applied at LC 50 ) was shorter (1.5–1.7 days) than that of control wasps. Both daily and total parasitism were significantly reduced (by 41.7, 48.3 and 60.1% for N, D and B, respectively) compared to control, as well as adult emergence in the F 1 generation. The ...