Biology and larval feeding impact of Hypena opulenta (Christoph) (Lepidoptera: Noctuidae): A potential biological control agent for Vincetoxicum nigrum and V. rossicum

Abstract

A classical biological control program has been initiated against the invasive European swallow-worts Vincetoxicum nigrum and Vincetoxicum rossicum in North America. The noctuid moth Hypena opulenta, discovered feeding on V. rossicum in forests of southeastern Ukraine, is currently under evaluation as a potential biological control agent. In this study the life cycle of H. opulenta and factors affecting diapause induction were evaluated. Additionally, larval impact of H. opulenta on Vincetoxicum spp. performance was tested to determine whether future screening is worthwhile. Adults of H. opulenta begin oviposition 2 days after emergence and produce approximately 600 eggs. Larvae develop through five larval instars and overwinter as pupae. Pupal diapause is facultative, resulting in at least two generations per year. Diapause induction is affected by photoperiod and seasonal changes in plant quality as evidenced by increasing diapause induction when larvae are grown under a short day photoperiod and on senescing plants in the fall. Feeding by two larvae per plant caused reductions in aboveground biomass to V. rossicum resulting in decreased reproductive output (flower, seedpod, and seed production). Only flower production of V. nigrum was negatively affected by larval feeding. The results of this study indicate that H. opulenta is a promising agent against forested populations of V. rossicum and warrants completion of host specificity testing and examination of population dynamics of H. opulenta. This practice of conducting impact assessments of herbivores that are apparent specialist feeders prior to conducting the full battery of host specificity tests should improve agent selection by reducing the costs associated with screening ineffective agents.