Dasineura sp. near capsulae (Diptera: Cecidomyiidae), a Candidate for Biological Control of Euphorbia esula Complex in North America

Abstract

The gall midge Dasineura sp. near capsulae Kieffer, whose larvae cause galls on flower buds of Euphorbia spp., was selected as a candidate agent for the biological control of leafy spurge, Euphorbia esula complex, a plant of Eurasian origin that has become a noxious weed in North America. Studies of a population of this midge associated with E. esula at S. Rossore, Pisa, Italy, indicated that this midge is univoltine. The adults appeared from early April until late May, living 2–4 d. Eggs were laid in the inner part of the bracts that cover the cyathium. The neonate larvae migrated into the cyathium, where they caused the formation of galls. The galls, appearing in early May, were produced by the enlargement and distortion of the cyathium and prevented seed production in the infested flowers. In late June and early July, mature larvae left the galls, fell to the ground where they entered the soil, hibernated until the following spring, and pupated a few days before the adults emerged. Host specificity tests of D. sp. near capsulae were made, using 48 test plants in 17 families. The midge oviposited on 13 test plants (all in the genus Euphorbia ) and the controls ( E. esula ). Ten of these test plants were in the subgenus Esula and one each in the subgenera Agaloma, Poinsettia, and Euphorbium . The midge completed development only on six of the test plants on which it oviposited, all in the subgenus Esula . The restricted host range of this midge suggests it would be safe to use as a biological control agent against leafy spurge in North America.