Exploratory surveys were conducted in Europe to locate potential biological control agents of Vincetoxicum nigrum and Vincetoxicum rossicum and to collect known specialist herbivores of Vincetoxicum hirundinaria (Abrostola asclepiadis, Chrysolina a. asclepiadis, Eumolpus asclepiadeus and Euphranta connexa). Development of the most abundant herbivores found attacking leaves, roots, and developing seeds was evaluated in the laboratory on three Vincetoxicum spp. Field surveys revealed that the highest diversity of herbivores was associated with the abundant and widespread V. hirundinaria. No new herbivores were reported from V. hirundinaria or V. nigrum, but the leaf‐feeding noctuid Hypena opulenta was recorded for the first time attacking V. rossicum and V. scandens in Ukraine. Based upon larval survival and development and adult fecundity, the leaf feeders A. asclepiadis, C. a. asclepiadis, and H. opulenta, perform better on V. nigrum and V. rossicum than on V. hirundinaria. Larval performance of the root feeder E. asclepiadeus followed a similar pattern, but adult fecundity of this insect did not vary among host plant species. Immature development time of the pre‐dispersal seed feeder E. connexa is similar among hosts, but larvae grow larger on V. nigrum and V. hirundinaria than on V. rossicum. All herbivores are promising biological control agents of Vincetoxicum in North America and we have prioritized host range testing with H. opulenta and E. asclepiadeus.

Vincetoxicum rossicum (Kleopow) Barbar and Vincetoxicum nigrum (L.) (Apocynaceae) are invasive perennial weeds in North America, for which Euphranta connexa (Fabricius) (Diptera: Tephritidae) is a potential biological control agent. Female E. connexa oviposit in seed pods of European Vincetoxicum species, and developing larvae consume the seeds. Mature larvae emerge and form overwintering puparia in the soil. To facilitate laboratory rearing and the synchronization of oviposition and larval activity with vulnerable stages of target and non-target plants, we investigated the effect of temperature on survival and development of E. connexa pupae and eggs. Field-collected pupae from Switzerland were overwintered in cool storage and in spring, and they were placed in constant-temperature treatments from 9.4 to 35°C. Adults emerged at temperatures from 11.8 to 27.3°C, and there was no evidence of pupal diapause. Rates of pupal development did not differ between sexes or among collection sites at altitudes ranging from 520 to over 1 700 m above sea level. From truncated normal models of development rate response to temperature, the estimated lower temperature threshold for pupal development was 4.2°C and development was most rapid at 25.8°C. When newly-laid eggs were exposed to constant temperatures from 11.8 to 30°C, hatch occurred at all temperatures. The estimated lower temperature threshold for egg development was 9.3°C, and the predicted temperature at which egg development was most rapid was 31.2°C. The models of pupal development suggest that E. connexa does not complete its life cycle at the highest altitude of our collection sites and that insects collected there were the result of dispersal from lower altitudes. The models predict that the northernmost North American sites where the insect might be released for biological control of invasive Vincetoxicum species are close to the northern limit for completion of the life cycle of E. connexa.