Effects of floral resources on the efficacy of a primary parasitoid and a facultative hyperparasitoid

Abstract

Resources added to agroecosystems to enhance biological control are potentially available to multiple members of the resident insect community—not only the biological control agents for which the resources are intended. Many studies have examined the effects of sugar feeding on the efficacy of biological control agents. However, such information is lacking for other, interacting species such as facultative hyperparasitoids, which may contribute to pest suppression but can also interfere with introduced biological control agents. Under greenhouse conditions, we tested the direct effects of sugar and nectar provisioning on the longevity, host-killing impact and offspring production of two pupal parasitoids associated with leek moth, Acrolepiopsis assectella: the introduced biological control agent, Diadromus pulchellus, and the native facultative hyperparasitoid, Conura albifrons. Adding sucrose, buckwheat or a combination of buckwheat and common vetch to a sugar-deprived system (potted leek plants in cages) increased parasitoid longevity and resulted in higher leek moth parasitism and mortality compared to water or common vetch treatments. However, the two parasitoid species exhibited a distinct temporal response to the treatments, likely influenced by differences in their life histories. This study provides insight into how integrating conservation biological control techniques could affect the success of a classical biological control programme.