Title: Response of invasive swallow-worts (Vincetoxicum spp.) to repeated artificial defoliation or clipping Authors
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 17, 2014
Publication Date: February 3, 2014
Citation: Milbrath, L.R., Ditommaso, A., Biazzo, J., Morris, S.H. 2014. Response of invasive swallow-worts (Vincetoxicum spp.) to repeated artificial defoliation or clipping. Weed Science Society of America Meeting Abstracts. http://wssabstracts.com/public/22/proceedings.html. Technical Abstract: The Eurasian vines pale swallow-wort (Vincetoxicum rossicum) (PSW) and black swallow-wort (V. nigrum) (BSW) are invasive perennials that have infested natural areas in the northeastern United States and southern Canada. A biological control program is being developed, though it is unclear how these perennial plants might respond to potential biological control agents as they experience little herbivore damage in North America. We are evaluating the effect of multiple seasons of artificial defoliation and clipping at different frequencies on the survival, growth, and reproduction of mature PSW and BSW plants grown under field conditions in Ithaca, NY. Root crowns of PSW and BSW were transplanted into a common garden in a 3-way factorial structure within a completely randomized experimental design with 5 replicates that included:  two target species (PSW, BSW),  eight damage treatments: 50 percent defoliation (all new leaves cut in half widthwise plus stem tips cut) or 100 percent defoliation once (July) or twice (June & July) each season; clipping stems 8 cm above soil level once (June), twice (June & July) or four times (May, June, July, Aug.) each season, and an undamaged control, and  year (repeated measures on above-ground [non-biomass] data or independently collected biomass samples after 1, 2, 4 & 6 seasons of damage). No plants died from damage over the past four years, and stem number increased from 5 (both species 2009) to 13 (BSW) or 17 (PSW) stems/plant in 2012. Plants clipped 4x per season had a lower root dry mass than other damage treatments; otherwise root mass increased over time, from 19 grams (2009 average) to 65 grams (2012). BSW root mass (27 grams on average) was less than PSW root mass (42 grams). Viable seed per BSW plant was less for plants clipped 2x or 4x per season than undamaged control plants; PSW also showed a similar but non-significant trend. Pale and black swallow-wort display a high tolerance to above-ground tissue loss, whether by artificial defoliation or clipping, in high-light environments without plant competition. Four clippings per season was the only type of damage that consistently reduced biomass and reproductive output. The continued annual increase in root dry mass and stem number calls into question the potential efficacy of a defoliating insect against field populations of swallow-worts.