A Simulation Study of Primary-, Clepto- and Hyperparasitism in Epinotia tedella (Lepidoptera, Tortricidae)

Publisher Website
Google Scholar
Abstract
(1) A model of combined parasitism in the spruce needleminer, Epinotia tedella (Cl.) is proposed. It covers the effect of two primary parasitoids, Pimplopterus dubius (Hgn.) and Apanteles tedellae Nix., a cleptoparasitoid, Campoplex cursitans (Hgn.), and a hyperparasitoid, Mesochorus silvarum Curt. The analysis of field data makes use of the log killing power/log parasitoid density relationship, and thereby, indirectly, the pseudo-interference submodel of parasitism. (2) The impact of individual species is analysed by means of computer simulations. The introduction of a second primary parasitoid is shown to decrease the equilibrium host density considerably, whereas the presence of hyperparasitoids improves stability. (3) The host-parasitoid system proves stable when the power of increase of the host is below seventeen, or below thirteen in the absence of clepto- and hyperparasitoids. (4) Parasitism is evaluated as an element in the complex of natural mortality factors acting on Epinotia tedella. The additional mortalities of the model are egg mortality due to Trichogramma evanescens Westw., larval mycosis caused by the fungus Paecilomyces farinosus (Holm.), and larval and pupal predation due to the elaterid Athous subfuscus Mull. Parasitism proves to be the superior agent in the reduction and stabilization of the host density. Thus, the removal of parasitism causes a ten-fold increase in the equilibrium host density. The effect of changed host fertility rate on equilibrium host density is hihgly significant at all combinations of mortality factors.