BIOLOGICAL CONTROL OF SWALLOW-WORTS, INVASIVE WEEDS OF THE NORTHEASTERN UNITED STATES
Location: Biological Integrated Pest Management Unit
Title: New biological information on the invasive swallow-worts (Vincetoxicum spp.)
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: February 6, 2012
Publication Date: February 6, 2012
Citation: Ditommaso, A., Mohler, C.L., Milbrath, L.R. 2012. New biological information on the invasive swallow-worts (Vincetoxicum spp.)[abstract]. Weed Science Society of America Meeting Abstracts. Paper No. 125. Available: (Http://wssaabstracts.com/public/9/abstract-125.html).
Vincetoxicum nigrum (L.) Moench [Cynanchum louiseae Kartesz & Gandhi] (black swallow-wort) and V. rossicum (Kleopow) Barbar. [Cynanchum rossicum (Kleopow) Borhidi] (pale swallow-wort) are herbaceous perennial vines in the Apocynaceae native to Europe. Both species are considered invasive in their introduced ranges in the northeastern U.S. and southeastern Canada, where they form dense stands, especially in high light environments such as old fields and field-woodland ecotones. These Vincetoxicum species were introduced into North America in the late 1800s, likely as ornamentals, but soon after escaped cultivation. Numerous rare and sensitive plant and animal species have been negatively impacted by their introduction. During the last decade, more than 40 refereed publications have focused on one or both of these species substantially enhancing our knowledge of their taxonomy, biology, ecology, and management. This is particularly true for V. nigrum, the least understood of the two species. New chemical and molecular information has clarified taxonomic inconsistencies such that the genus Vincetoxicum is now considered more closely related to the genus Tylophora than Cynanchum as previously thought. Moreover, the genus Vincetoxicum is now included in the Apocynaceae rather than the Asclepiadaceae, as the three subfamilies of this latter family, including the Asclepiadoideae, were transferred intact into the Apocynaceae. New information from European and North American populations confirms the diploid and tetraploid nature of V. rossicum and V. nigrum plants respectively, suggesting that hybridization is unlikely in regions where their ranges overlap. Preliminary bioclimatic modeling indicates that expansion of the two species south and west of their current range is likely. New data have provided a better understanding of factors that allow for successful establishment and spread of the two vines including seedling survival, vegetative expansion, and effects of allelochemicals and intra- and inter-specific competition. Additional morphological, physiological and life history differences between the two species have been elucidated. Management options using herbicidal, cultural, and/or biological tactics have also been intensively studied during the last decade. The herbicides triclopyr, glyphosate, and imazapyr have shown most promise. Mowing may be effective in reducing populations in sub-optimal habitats such as forest understories, but is generally not recommended in high density habitats like old fields. Substantive advances have been made in the search for biological control agents to suppress Vincetoxicum populations in their introduced range. Promising non-native insect candidates include defoliating moths in the genera Abrostola and Hypena. Root-feeding beetles in the genus Chrysochus appear to present a risk to native milkweeds. Other insect species continue to be screened. The pathogenic fungi Colletotrichum lineola and Sclerotium rolfsii have recently been isolated from diseased plants and may hold promise. The increased knowledge and research attention afforded these two Vincetoxicum species in the last decade has resulted in their classification as ‘noxious weeds’ in some U.S. and Canadian jurisdictions including several New England States.