Identification and impact of hyperparasitoids and predators affecting Cyzenis albicans (Tachinidae), a recently introduced biological control agent of winter moth (Operophtera brumata L.) in the northeastern U.S.A.

Abstract

The success or failure of an introduced biological control agent may depend on its rate of mortality from disease, predation, and hyperparasitism. Cyzenis albicans Fallén (Diptera: Tachinidae) was introduced to the northeastern U.S. as a biocontrol agent of the invasive species winter moth, Operophtera brumata L. (Lepidoptera: Geometridae). This study aimed to determine the rates of mortality from predation by generalist ground predators and hyperparasitism of C. albicans puparia, identify any hyperparasitoids, and assess the impact of predation and hyperparasitism on the potential success of C. albicans in controlling the winter moth. Mortality of C. albicans puparia was primarily due to predation, but there was also hyperparasitism. Predation and parasitism of C. albicans puparia were consistently high across the six study sites and two years of study, but somewhat lower than was reported from British Columbia, where successful establishment of C. albicans in the 1970s was followed by a decrease in winter moth densities. In this study, three genera of ichneumonid hyperparasitoids were detected and identified using a combination of morphological and molecular approaches: Phygadeuon (1 species), Pimpla (2 species), and Gelis (2 species), all of which contain species with broad host ranges and were likely acting as facultative hyperparsitoids. We conclude that while total mortality of C. albicans puparia is high, it is unlikely to have a significant effect on biological control of winter moth in this system, although it may explain why C. albicans has been slow to establish in this region. Our study emphasizes the importance of assessing the mortality of introduced biological control agents caused by native predators and hyperparasitoids.