Long-term effects of sub-lethal doses of biocide (25, 50, 100 and 200 micrograms/ml) from B. sphaericus 1593 M on feeding, growth and reproduction of L. griseus were studied. The deleterous effects of the biocide include: reduced feeding, retarded growth, delayed maturity, reduction in fecundity, and decrease in protein content of the ovary. The effects are convincingly dependent on biocide dose and exposure duration. Extensive use of the biocide may bring a population depletion of non-target species even at sub-lethal concentrations. The possible mode of action of biocide is discussed.