UC Riverside

The leaffooted bug, Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae) is a key pest of almonds and pistachios in California, USA. With limited monitoring strategies and no economic thresholds developed, the use of broad-spectrum insecticides remains the primary control tactic for leaffooted bug. In pursuit of more sustainable management options, a series of experiments were carried out to evaluate if floral resource provisioning could enhance biocontrol of leaffooted bug by the egg parasitoid Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae). The first portion of this work identified key life history traits of H. pennsylvanicus on eggs of its host L. zonatus, and evaluated the role of food deprivation on parasitoid reproductive performance. The second section assessed how diet quality influenced parasitoid nutrient acquisition and reproductive fitness, and evaluated whether groundcovers could be used to bolster natural enemy populations, and in turn, improve biological control of L. zonatus in orchards. Hadronotus pennsylvanicus exhibited suitable demographic and reproductive traits as a biocontrol agent of L. zonatus. However, adult diet had a direct influence on the reproductive fitness of female wasps. When given frequent access to a honey diet, female parasitoids lived significantly longer and parasitized more host eggs compared to starved individuals. Behavioral assays demonstrated that satiated females spent more time interacting with host eggs and tended to less frequently divert from oviposition behavior. The quality of adult diet also influenced the reproductive fitness of female H. pennsylvanicus. My data indicated that diets containing high sucrose concentrations increased female longevity and offspring production two-fold in comparison to individuals fed a low sucrose diet. Subsequent laboratory assays demonstrated that buckwheat flowers provided a significantly greater benefit to female longevity than oat, mustard, or cowpea flowers. However, in field trials, flowering groundcovers of any type did not enhance resident H. pennsylvanicus populations nor the biological control of L. zonatus. This dissertation project highlighted the role of diet on parasitoid reproductive fitness, and provided insight into the prospects and limitations of using floral resources for enhancing biological control of L. zonatus by the egg parasitoid H. pennsylvanicus.