The impact of the plant growth regulator gibberellic acid (GA(3)) on parasitoid development and reproduction was examined using the endoparasitoid Apanteles galleriae Wilkinson (Hymenoptera: Braconidae). The effects of GA(3) were assessed by rearing A. galleriae on hosts fed the growth regulator and then measuring a several life history traits: developmental time from egg to adult, adult longevity, body sizes, fecundity, and sex ratios. GA(3) treatment yielded dose-dependent changes in adult longevity and duration of development. For example, at GA(3) doses > 10 ppm, the life span of both male and female adult wasps decreased by 19-23 d in comparison with parasitoids that developed on GA(3)-free hosts. Likewise, the length of development from egg to adult emergence significantly increased when A. galleriae developed on hosts fed the growth regulator at doses > 200 ppm. In contrast, GA3 did not seem to alter adult body sizes, sex ratios, or fecundity, with the exception that F-2 progeny production decreased by > 40% at high concentrations (>= 200 ppm). The potential significance of plant growth regulators on natural enemies used in integrated pest management programs is discussed.