Biological Effects and Toxicokinetics of DIM BOA in Diadegma terebrans (Hymenoptera: Ichneumonidae), an Endoparasitoid of Ostrinia nubilalis (Lepidoptera: Pyralidae)

Abstract

2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), the major hydroxamic acid present in corn, was tested for its effect on the endoparasitoid of Ostrinia nubilalis (Hubner), Diadegma terebrans (Gravenhorst). The compound was fed to O. nubilalis (0.3 mg DIMBOA/g diet), and the response of the parasitoid was measured in terms of development time and weight and mortality at the pupal and adult stages. DIMBOA increased mean time to pupation and mean time to adult emergence for both males and females. Male and female pupal and adult weights decreased in the presence of DIMBOA. DIM BOA also was associated with increased mortality of parasitized O. nubilalis larvae, but final percentage parasitization was significantly increased by the compound (28.1 versus 41.0%). Parasitoids pupating from O. nubilalis larvae fed a diet containing 3H-DIMBOA showed levels of 3H compounds (determined by measuring the level of tritium in the samples) over twice as high (per gram weight) as the O. nubilalis pupae. At adult emergence, higher levels of 3H compounds were found in the cocoon and meconium than in the adult; higher levels were present in males than in females.