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GALL INDUCTION BY PEGOMYA CURTICORNIS (STEIN) (DIPTERA: ANTHOMYIIDAE) WITHIN THE ROOTS OF SPURGES EUPHORBIA VIRGATA WALDST. AND KIT. AND E. ESULA L. (EUPHORBIACEAE)

Published online by Cambridge University Press:  31 May 2012

Joseph D. Shorthouse
Affiliation:
Department of Biology, Laurentian University, Sudbuy, Ontario, Canada P3E 2C6
Andre Gassmann
Affiliation:
CAB International Institute of Biological Control, European Station, CH-2800, Delémont, Switzerland

Abstract

The anthomyiid fly Pegomya curticornis (Stein), introduced into Alberta from Europe for the biocontrol of leafy spurge (Euphorbia esula L.), normally induces simple galls on subterranean stems. Here we describe the anatomy of galls collected in Europe that had been induced by P. curticornis on horizontal roots of spurges. Four mature galls were found on the roots of E. virgata Waldst. and Kit. and 10 on the roots of E. esula. Tissues of the root galls were composed of gall parenchyma that had proliferated from feeding sites near the outside edge of secondary xylem. It is assumed that some larvae inadvertently tunnel beyond the base of stems into the roots and that similar galls will form on Alberta spurges.

Résumé

L’anthomyie Pegomya curticornis (Stein), importée d’Europe et introduite en Alberta pour assurer le contrôle biologique de l’euphorbe Euphorbia esula L., forme normalement des galles simples sur la partie souterraine des tiges. Nous décrivons ici l’anatomie de galles trouvées en Europe et causées par P. curticornis sur les racines horizontales d’euphorbes. Quatre galles mûres ont été trouvées sur les racines d’E. virgata Waldst. et Kit. et 10 sur les racines d’E. esula. Les tissus des galles radiculaires étaient composées de parenchyme de galle provenant des points d’alimentation situés aux abords de la zone externe du xylème secondaire. Il semble que certaines larves s’aventurent au-delà de la base des tiges et creusent des tunnels jusque dans les racines et il faut s’attendre à trouver des galles semblables sur les euphorbes d’Alberta.

[Traduit par la Rédaction]

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1994

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