Performance of potential European biological control agents of Vincetoxicum spp. with notes on their distribution

Abstract

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.

Evaluation of Host Range and Larval Feeding Impact of Chrysolina aurichalcea asclepiadis (Villa): Considerations for Biological Control of Vincetoxicum in North America

“…native to North America. There are four additional agents under consideration for the biological control of Vincetoxicum (Weed et al 2011b). Among these, the leaf-feeding noctuids Abrostola asclepiadis (Denis and Schiffermü ller) and Hypena opulenta (Christoph) look most promising because they only attack members of the genus Vincetoxicum (Weed 2010a, Hazelhurst 2011.…”

“…We attempted to screen all replicates of a plant species during the same year but this was not always possible. Vincetoxicum nigrum, V. rossicum, or V. hirundinaria were used as controls because larval survival is similar among these plant species (Weed et al 2011b). The suitability of host plants for development was evaluated by counting the number of larvae surviving to pupation and calculating the average time to pupation for all individuals per cup.…”

“…Specimens from Ticino, Switzerland have only been observed attacking V. hirundinaria (Weed et al 2011b). Similar to other C. aurichalcea, movement and host selection behavior of C. a. asclepiadis are not well understood.…”

“…Annual herbicide treatment only produces temporary results (Lawlor andRaynal 2002, Averill et al 2008) and application costs and risk to nontarget species has promoted interest in alternative control techniques. A classical biological control program was initiated for swallow-worts in North America in 2006 (Tewksbury et al 2002, Weed et al 2011b). During surveys for potential biological control agents of Vincetoxicum in Europe, the leaf beetle Chrysolina aurichalcea asclepiadis (Villa) was observed attacking V. hirundinaria in southern Switzerland (Weed et al 2011b).…”

“…A classical biological control program was initiated for swallow-worts in North America in 2006 (Tewksbury et al 2002, Weed et al 2011b). During surveys for potential biological control agents of Vincetoxicum in Europe, the leaf beetle Chrysolina aurichalcea asclepiadis (Villa) was observed attacking V. hirundinaria in southern Switzerland (Weed et al 2011b). It was later discovered that this beetle successfully develops on V. nigrum and V. rossicum, prompting further evaluation as a biological control agent (Weed et al 2011b).…”