GALL INDUCTION BY PEGOMYA-CURTICORNIS (STEIN) (DIPTERA, ANTHOMYIIDAE)WITHIN THE ROOTS OF SPURGES EUPHORBIA-VIRGATA WALDST AND KIT AND E-ESTULA L (EUPHORBIACEAE)

The anthomyiid fly Pegomya curticornis (Stein), introduced into Albert a 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 fou nd on the roots of E. virgata Waldst. arid Kit. and 10 on the roots of E. esula. Tissues of die root galls were composed of gall parenchyma that had proliferated from feeding sites near die outside edge of seco ndary xylem. It is assumed that some larvae inadvertently tunnel beyon d the base of stems into die roots and that similar galls will form on Alberta spurges.