The flower-head feeding fly Acinia picturata (Diptera: Tephritidae) was deliberately introduced from Mexico into Hawaii in 1959 for biological control of the exotic weed Pluchea odorata (Snow) (Asteraceae). Neither field efficacy nor possible non-target effects of the fly have been evaluated in the 40 years since the introduction. We assessed the impact of the fly on both its target host and on 7 non-target plant species. The impact on the target weed was limited, with only 5 – 13% of the developing seeds in P. odorata flowerheads being destroyed by larval feeding. We did not detect any host range expansion of A. picturata onto flowerheads of 2 exotic or 5 endemic non-target plant species in the family Asteraceae. [Full Text]