Interpreting host-test results for classical biological control candidates: Can the study of native congeners improve the process?

Biology of Invasive Plants 3.Vincetoxicum nigrum(L.) Moench andVincetoxicum rossicum(Kleopow) Barbarich

“…Pupal diapause is induced in H. opulenta at a threshold photoperiod of 15 h 35 min (Jones et al 2020). Two generations per summer have been shown to occur at release sites >42°N latitude when H. opulenta was experimentally released by late June (daylength of 15 h 20 min or more; Alred et al 2022b;Jones et al 2020). However, the threshold photoperiod may result in only one generation per summer at more southern latitudes in North America, reducing the potential impact of H. opulenta on Vincetoxicum infestations.…”

“…Screening of C. asclepiadeus was halted for several years because larvae can develop on some non-target species, including North American Asclepias species (Bourchier et al 2013). However, a recent study advocated reevaluating C. asclepiadeus as a potential agent (deJonge et al 2020). European field tests have been underway since 2018 to better characterize whether it will attack non-target species under field conditions (LRM, personal observation).…”

“…Adult females lay single eggs, and the larvae do not aggregate, reducing the amount of feeding damage inflicted on individual plants unless H. opulenta populations reach high levels throughout an area (Bourchier et al 2019). Pupal diapause is induced in H. opulenta at a threshold photoperiod of 15 h 35 min (Jones et al 2020). Two generations per summer have been shown to occur at release sites >42°N latitude when H. opulenta was experimentally released by late June (daylength of 15 h 20 min or more; Alred et al 2022b;Jones et al 2020).…”