New records document Cystiphora sonchi (Vallot) (Diptera: Cecidomyiidae) and associated parasitoids (Hymenoptera) in the continental United States

Abstract

A gall midge, Cystiphora sonchi (Vallot, 1827) (Diptera: Cecidomyiidae), is reported for the first time in the continental United States of America from the states of Minnesota, North Dakota, and South Dakota. The gall midge is an obligate parasite of Sonchus L., including perennial sowthistle, Sonchus arvensis L., a weed that was the impetus for earlier releases of C. sonchi as a biological control in Canada. Patches of S. arvensis were commonly infested with C. sonchi, and often leaves were densely galled. Dissections of galled leaves led to the novel finding of multiple C. sonchi larvae in some individual galls. In addition, three parasitoids emerged from galls sampled in South Dakota: Aprostocetus cf. atticus Graham, Ceraphron sp., and a possible new species of Lyrcus Walker. Further research is warranted to determine the geographic extent of C. sonchi and its parasitoids in the USA, and to determine the impact of C. sonchi on its weedy hosts.