Hyssopus pallidus (Askew): Biology, clutch size and potential in the biological control of the codling moth

Hyssopus pallidus (Hymenoptera: Eulophidae) was recently discovered attacking the codling moth in France and has been considered as a potential candidate for introduction into California for the biological control of this fruit-boring pest of apples, pears and walnuts. Studies of its general biology revealed that it is a gregarious synovogenic idiobiont ectoparasitoid that can attack a wide range of larval stages of the host. It has a fecundity of 170 large eggs, a longevity of 55 days at 22-24{dollar}{bsol}sp{bsol}circ{dollar}C with access to honey, and an elaborate host handling behavior.; Manipulative experiments showed that H. pallidus has the ability to adjust its clutch size in relation to host quality, represented by host size and host age; to host condition, represented by previous parasitism by conspecifics and Ascogaster quadridentata (Hymenoptera: Braconidae); and to host relative abundance, represented by frequency of host encounters. A more detailed study of the competitive interaction of H. pallidus and A. quadridentata revealed that larvae parasitized by A. quadridentata are better quality hosts for H. pallidus, probably due to an improved nutritional status of the host, and can support almost twice as many female progeny as healthy host larvae of comparable size.; Adding some complexity to simple difference equation models increases their level of realism and their utility as predictive tools in biological control projects. We show that the addition of age structure to the host population is essential to estimate the impact of different parasitoid guilds and to consider how best to minimize damage caused by the most destructive developmental stages of the host.; Using a novel age-structured host-multiparasitoid model, along with parameter estimates from the literature and current experimental results, we show that the introduction of H. pallidus into California would be beneficial to the present system that contains only the codling moth and A. quadridentata. A sensitivity analysis of the model, to include variation in each of the parameter values in turn, suggests that the predicted reduction in late instar larvae is robust.