200 Session 4 Target and Agent Selection Towards Biological Control of Swallow-Worts: The Ugly, the Bad and the Good R. Sforza1, M. Augé1, M.-C. Bon1, R. Dolgovskaya2, Y. Garnier1, M. Jeanneau1, J. Poidatz1, S. Reznik2, O. Simonot1, M. Volkovitch2 and L. R. Milbrath3 1USDA-ARS European Biological Control Laboratory, CS 90013 Montferrier sur Lez, 34988 St Gély du Fesc, France [email protected] 2Zoological Institute, Anglijskij prospect, 32, St.Petersburg 190121, Russia 3USDA Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, 538 Tower Road, Ithaca, NY 14853, USA Abstract Native to Eurasia, swallow-worts (“the ugly:” Vincetoxicum rossicum (Kleopov) Barbarich and V. nigrum L. - Apocynaceae) have invaded forested landscapes and prevented native plant regeneration in eastern North America. We first aimed to understand where the invasive populations of both species come from, and then evaluated the impact of potential biological control agents (BCAs). The following phytophagous BCAs have been studied since 2009: Chrysochus asclepiadeus (Pallas) (Col., Chrysomelidae), Abrostola asclepiadis (Denis & Schiffermuller) and Abrostola clarissa (Staudinger) (Lep., Noctuidae). Adults of the beetle feed on leaves while larvae are root feeders, and Abrostola spp. larvae are foliage feeders. Genetically, none of the native V. nigrum populations analyzed to date possesses exactly the major multilocus genotype detected in the invasive North American populations, in contrast to V. rossicum, for which source populations of the invasion are found to be in Ukraine. We performed choice and no-choice specificity tests with French and Russian populations of C. asclepiadeus. We evaluated adult herbivory in no-choice tests on three Vincetoxicum spp., as controls, and seven Asclepias spp.: C. asclepiadeus fed on controls but also on Asclepias tuberosa L., a monarch butterfly host plant. Choice tests revealed no herbivory outside the genus Vincetoxicum. Larval herbivory in choice tests was noticed on all controls, plus A. tuberosa and Asclepias syriaca L. Similar results were obtained for both populations of C. asclepiadeus. Although C. asclepiadeus has a severe impact on swallow-worts, herbivory on several Asclepias spp. lead us to consider it a “bad” BCA. No-choice tests with larvae of Abrostola asclepiadis from France revealed that they died in 5d on all the Asclepias spp., but developed to pupa in 23d on Vincetoxicum hirundinaria Medik., in 20.6d on V. rossicum, and only reached the 3rd instar in 17.8d on V. nigrum. Similar results were obtained with Abrostola clarissa of Russian origin. Thus, data with Abrostola spp. appear promising, and we consider the two Abrostola species to have good potential as BCAs against all genotypes of swallow-worts. XIII International Symposium on Biological Control of Weeds - 2011.