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

Abstract

AbstractThe 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.