ABSTRACT: The toxicity and biological effects of sub-lethal concentrations of the microbial insecticide vertimec (product of Streptomyces avermitilis-Avermectin-1.8% w/v) on pink bollworm (PBW), Pectinophora gossypiella larvae were evaluated under laboratory conditions. The effects of vertimec on some biological activities of PBW larvae were recorded . The tested compound prolonged the larval period (21.97 days) than the control (17.49 days). Also, the larval weight of the 2nd instar larvae was affected, where the average weight was 2.78 mg in control, while it was significantly decreased to 0.47 mg in larvae treated with vertimec. In contrast, weight of the 4th larval stage was significantly increased in vertimec treatment (28.86 mg) . The pupal duration, pupal weight and pupal mortality were not significantly affected, whereas the pupation percentage was inhibited due to the larval treatment. Obviously, the earlier treatment of newly hatched larvae of PBW with vertimec was extended to the produced moths. Vertimec gave 87.06 % moth emergence compared with the control (98.36%). Sex ratio was directed to the male side (66.41%). In addition, vertimec affected the oviposition periods, where adult longevity and fecundity of the emerged females had low reproductive capacity compared to control. Furthermore, vertimec affected the five main parameters associated with a fertility life table (the generation time (T), net reproductive rates (RO), doubling time (DT), intrinsic rate of increase (rm) and finite rate of increase (erm). In conclusion, vertimec treated PBW larvae had the lowest of population growth parameters as indicated by the long developmental time (42.67 days), low net reproductive rate (20.24 ♀/♀), and low survival of immature stages as reflected in a lower value of rm (0.07 ♀/♀/day). Generally, vertimec proves to be an effective bio-insecticide against developmental stages of PBW and could be an excellent fit into IPM/ICM programs on cotton plants by the Ministry of Agriculture after successful field experiments.