Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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EMERGENCE AND PERFORMANCE OF TWO SWALLOW-WORT SPECIES ON
SOILS OF VARYING pH AND ORIGIN. L.C. Magidow, A. DiTommaso, Cornell Univ.,
Ithaca, NY, L. Milbrath, USDA-ARS U.S. Plant, Soil and Nutrition Laboratory, Ithaca,
NY, and C.L. Mohler, Cornell Univ., Ithaca, NY.
ABSTRACT
Two alien vines, pale swallow-wort, (Vincetoxicum rossicum) and black swallowwort
(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. The 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.
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