Parasitism of native parasitoids on Procecidochares utilis Stone (Tephritidae, Diptera), a biocontrol agent against the invasive exotic weed Eupatorium adenophorum Spreng (Compositae) in southwest China.
To investigate the native parasitoid guild attacking the fruit fly, Procecidochares utilis, an introduced biocontrol agent against the exotic crofton weed Eupatorium adenophorum [Eupatorium trapezoideum] in southwest China, we took samples of galls induced by the fruit fly from two habitats, the open field and forest, and reared half of the samples for emergence of the fruit fly or parasitoids and dissected another half for parasitism. Six species of solitary parasitoids emerged from galls with a combined parasitism of over 70%, among which three parasitoids, Torymoides kiesenwetteri, Bracon sp. and Eurytoma trypeicola, accounted for most of the parasitism. Even though Eupatorium adenophorum grew better (as measured by plant height and number of branches) and the infestation rate of galls was higher in the open field than in the forest, the parasitism of each parasitoid and total parasitism did not significantly differ between two habitats. The number of emerged parasitoids per gall increased significantly with the gall size as measured by the horizontal diameter of galls.