Long-term Spread and Control of Invasive, Common Reed (Phragmites australis) in Sheldon Marsh, Lake Erie

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2008-12

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Abstract

In 2001 the Ohio Department of Natural Resources (ODNR) initiated a long-term, herbicide-spraying control program of Phragmites australis (common reed), a highly invasive perennial grass, in Sheldon Marsh on Lake Erie’s south shoreline. Controlling reed is a priority of many wetland managers because habitat homogenization from reed expansion may adversely affect wildlife habitat and waterfowl. Reed has historically been a minor part of wetland plant communities of the Laurentian Great Lakes but has spread rapidly since 2000 when lake water levels dropped. Here we examined ODNR records and aerial photographs using ArcGIS software and planimetry from 2000 to 2007 to (1) track annual changes in reed localities and areal coverage, (2) compare short-term effectiveness of glyphosate (Glypro® and AquaNeat®) and imazapyr (Habitat®) herbicides, and (3) estimate control costs. Reed first appeared in a small, isolated patch in 1998 but expanded to comprise approximately 18 percent of the marsh’s emergent vegetation by 2001. Annual change in areal cover was not related to minor changes in already low Lake Erie water levels. However, reed amount decreased from 6.7 ha (= 14.8 percent of emergent vegetation) in 2004 to 2.5 ha in 2007 after a two- to three-fold annual increase in amount of herbicide used. Short-term, post-spraying necrosis (browning) was slower for Phragmites treated with a five percent Habitat® solution than with a 30 percent AquaNeat® solution. Slowed necrosis presumably prolongs photosynthesis and plant nutrient uptake and delays habitat deterioration for some wildlife, but provides time for vegetative spread. Seven years of herbiciding have contained reed to approximately six percent of the emergent plant cover. Estimated control expenditures from 2003 to 2007 were \$8475 USD (average approximately \$1700/year); a small cost to maintain system ecological diversity.

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Author Institution: Department of Evolution, Ecology, and Organismal Biology, The Ohio State University

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The Ohio Journal of Science, v108, n5 (December, 2008), 108-112.