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Title: Emergence and Performance of Two Swallow-wort Species on Soils of Varying pH and Origin

item Milbrath, Lindsey

Submitted to: Proceedings of Northeastern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 11/20/2006
Publication Date: 1/2/2007
Citation: Magidow, L.C., Ditommaso, A., Milbrath, L.R., Mohler, C.L. 2007. Emergence and Performance of Two Swallow-wort Species on Soils of Varying pH and Origin. Proceedings of Northeastern Weed Science Society. p.12.

Interpretive Summary:

Technical Abstract: Two alien vines, pale swallow-wort, (Vincetoxicum rossicum) and black swallow-wort (V. nigrum), are increasingly problematic invaders in the Northeastern U.S. and Southeastern Canada. These herbaceous perennial species aggressively colonize and rapidly dominate forest understories, old fields, rare alvar (shallow limestone barren) communities, and other native ecosystems throughout the region. Swallow-worts have been difficult to control by mechanical and chemical methods. In 2004, a biological control program was initiated by the USDA-ARS to supplement these approaches. The program will introduce insects and/or pathogens from the plants' native European ranges in order to suppress these weedy vines. To biologically control swallow-wort most effectively, we must understand what factors affect their current and potential distributions within North America. This experiment examines how two edaphic factors that may play a part in swallow-wort distribution, pH and soil type, affect the performance of these species. In this microplot field experiment, soil and seeds were collected from two locations in NY State that were heavily infested with either pale swallow-wort (Benson-Wassaic silt loam) or black swallow-wort (Hollis sandy loam) and then subject to the same field conditions in Ithaca, NY. Each soil type was amended to attain three pH levels (original level, 4.5, and 8.0). The soil was then placed into drained pots, and in late fall of 2005 and 2006 swallow-wort seeds were scattered on the surface of the treated soil. Seedling emergence was monitored, plants were thinned to six per pot, and pots were weeded throughout the season. Before the first hard frost, plants and roots were harvested to determine above- and below-ground biomass. Preliminary data indicate greater emergence and establishment of both swallow-wort species at the higher pH levels and for both soil types. Surprisingly, some plants produced mature follicles during the first growing season. Data from the 2006 cohort of seeds will be collected at the end of the 2007 growing season. These data will also be compared to soil pH levels of sites with established swallow-wort species throughout NY State.