Entomophaga

, Volume 28, Issue 4, pp 379–386 | Cite as

Superparasitism and host discrimination byEphedrus cerasicola [Hym.: Aphidiidae], an aphidiid parasitoid ofMyzus persicae [Hom.: Aphididae]

  • T. Hofsvang
  • Eline B. Hågvar
Article

Abstract

Myzus persicae (Sulzer) at different densities (1 to 120 aphids) on a paprika plant in a 1.8 dm3 cage were exposed at 21°C to single females of the parasitoidEphedrus cerasicola Stary. Three different exposure periods were used: 1 hr, 6 hrs, 24 hrs. The aphids were dissected 6 days after parasitization.

Superparasitism was measured as number of hosts superparasitized and number of parasitoid larvae per aphid. It attained a maximum around host density=5 and decreased with increasing host density and decreasing exposure time. Almost no superparasitism occurred during the 1st hour.

A non-random larval distribution indicated thatE. cerasicola discriminates between unparasitized and parasitized aphids, but probably not between aphids with different numbers of parasitoid eggs.

Larvae in superparasitized aphids developed slower than single larvae. The supernumerary larvae died during the 1st instar, probably killed by chemical means since no physical attacks between larvae have been observed.

Keywords

Cage Exposure Time Plant Pathology Exposure Period Host Density 

Résumé

DesMyzus persicae (Sulzer) à différentes densités (1 à 120 pucerons) sur une plante de paprika ont été exposés dans une cage de 1,8 dm3, à 21°C, à une femelle du parasitoideEphedrus cerasicola Stary', pendant 3 périodes: 1 h, 6 h, 24 h. Les pucerons ont été disséqués 6 jours après le parasitisme. Le superparasitisme a été évalué, d'après le nombre d'hôtes ayant plusieurs parasites et le nombre de ceux-ci par puceron. Il a atteint son maximum pour une densité en hôtes de l'ordre de 5 et a diminué avec l'augmentation de la densité en hôtes et avec la diminution du temps d'exposition. Il n'y a pratiquement pas de superparasitisme pendant la lère heure.

La distribution non au hasard de ses larves montre queE. cerasicola distingue entre les pucerons parasités et non parasités, mais vraisemblablement pas entre des pucerons ayant des nombres différents de parasites.

Les larves se développent plus lentement dans les pucerons superparasités qu'en cas de présence d'un seul individu. Les larves surnuméraires meurent au ler stade, probablement tuées par des médiateurs chimiques, puisqu'il n'a été observé aucune attaque physique des larves entre elles.

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Copyright information

© Lavoisier Abonnements 1983

Authors and Affiliations

  • T. Hofsvang
    • 1
  • Eline B. Hågvar
    • 2
  1. 1.Agricultural EntomologyAgricultural University of NorwayNorway
  2. 2.Department of ZoologyAgricultural University of NorwayNorway

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