PHENOLOGY OF THE NATIVE PARASITOID SINOPHORUS MEGALODONTIS (HYMENOPTERA: ICHNEUMONIDAE) RELATIVE TO ITS INTRODUCED HOST, THE PINE FALSE WEBWORM (HYMENOPTERA: PAMPHILIIDAE)

Abstract

The parasitoid Sinophorus megalodontis Sanborne is a univoltine endoparasitoid that attacks larvae of the pine false webworm, Acantholyda erythrocephala (L.). The morphologies of the egg, instar 1, and cocoon are described. Adult-emergence and Malaise traps were used to examine the patterns of adult activity in Ontario. Adults emerged from the soil over 17 d, in late May and early June, and the median emergence of males preceded that of females by 3.5 d. The sex ratio of emerging adults was approximately 1:1. Malaise traps collected more adults than did emergence traps and also provided information on adult flight period, but collections were biased towards captures of males. Dissections indicated that S. megalodontis oviposited in all instars of the host and that temporal and spatial variations occurred in coincidence with host instars. Encapsulation and superparasitism limited effectiveness of the parasitoids in reducing host populations. At the end of the larval period, the parasitism rate was 17.1%, but encapsulation reduced the effective rate to 9.0%. Superparasitism was observed in 4.8% of the host larvae. There was some indication that parasitism resulted in retardation of host development. Later-dropping host larvae had a significantly greater incidence of parasitism. The host is an introduced insect from Europe, whereas the parasitoid is likely endemic to North America. Few North American parasitoids attack this introduced species, and S. megalodontis appears limited in its ability to reduce the size of pine false webworm populations. Consequently, pine false webworm is a suitable candidate for classical biological control attempts with introduced parasitoids from Europe.

Sex Pheromone of the Pine False Webworm Acantholyda erythrocephala

“…Outbreaks in the U.S. and Canada can encompass thousands of hectares and persist for 20 yr or more (Asaro and Allen 1999;Allen 2000, personal observation), resulting in a growth reduction and increased mortality of host trees (MiddleKauff 1958;Syme 1981;Moody 1990;Lyons 1994;Asaro and Allen 2001;Mayfield et al 2005). Numerous strategies considered as a means of control for this pest have met with variable success including: application of synthetic pesticides (Lyons et al 1993), natural toxins such as neem extracts (Helson et al 1999;Lyons et al 1996Lyons et al , 1998Lyons et al , 2003, biological control (Wilson 1984;Lyons 1999;Kenis and Kloosterman 2001;Thompson et al 2003). However, many of these strategies require precise knowledge of the distribution and phenology of PFW over large tracts of forest.…”