Effects of Indol-3-Acetic Acid on Biological Parameters of the Larval Endoparasitoid Apanteles galleriae (Hymenoptera: Braconidae)

Abstract

Abstract The nontarget effects of the plant growth regulator indol-3-acetic acid (IAA) on parasitoid development and reproduction were examined using the endoparasitoid Apanteles galleriae Wilkinson (Hymenoptera: Braconidae). The effects of IAA were assessed by rearing A. galleriae on hosts fed different doses of the growth regulator and then measuring a range of life history traits such as immature developmental time, adult longevity, body size, fecundity, and sex ratios in F1 and F2 generations. Wasp development from egg to adult took 27–47 d. However, adult emergence of parasitoids reared on hosts exposed to IAA doses required 14–24 d longer than controls to complete development at doses >200 ppm. Longevity of IAA-treated adult wasps was lower than that of controls at any dose. For example, at IAA doses >200 ppm, the life span of both male and female adult wasps decreased >50% compared with parasitoids that developed inside IAA-free hosts. Adult length also decreased at 500 and 1,000 ppm with respect to the control and lesser dosages. The total number of progeny decreased >50% and female sex ratio increased at doses >200 ppm compared with controls. Our results showed that the developmental biology of parasitoids exposed indirectly to IAA might be affected by high doses.