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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICALLY BASED INTEGRATED MANAGEMENT OF INVASIVE AQUATIC AND RIPARIAN WEEDS

Location: Exotic and Invasive Weeds Research

Title: Evaluation of Glyphosate for Managing Giant Reed (Arundo donax)

Authors
item Spencer, David
item Tan, W - UC DAVIS
item Liow, Pui Sze
item Ksander, Gregory
item Whitehand, Linda
item Weaver, S - SAN JOAQUIN RIVER TRUST
item Olson, J - SONOMA ECOLOGY CENTER
item Newhouser, M - SONOMA ECOLOGY CENTER

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 25, 2008
Publication Date: July 31, 2008
Citation: Spencer, D.F., Tan, W., Liow, P., Ksander, G.G., Whitehand, L.C., Weaver, S., Olson, J., Newhouser, M. 2008 Evaluation of Glyphosate for Managing Giant Reed (Arundo donax). Journal of Invasive Plant Science and Management. 1:248-254

Interpretive Summary: Giant reed is an invasive plant of riparian habitats. There is little data on the efficacy of different concentrations of glyphosate or imazapyr which can be used to select an appropriate application regime. We conducted two field experiments and monitored a site where imazapyr had been applied. Leaf chlorophyll content and the proportion of living stems declined significantly following treatment with 1.5% or greater solutions of glyphosate. New stems were observed the spring following treatment for plants treated with 1.5% glyphosate. No new stems were observed for plants treated with either 3% or 5% glyphosate. Plants treated with 1.5% imazapyr had reduced leaf chlorophyll content after treatment but recovered the following spring. Imazapyr treatment did not significantly reduce the proportion of living stems or prevent the production of new stems during the spring following treatment. These results indicate that 3% or 5% foliar applications with glyphosate were effective and consistent treatments for killing giant reed with a single late season application. This result is important if the goal is to minimize the number of treatments, reduce labor costs, and minimize impacts on sensitive habitats by reducing the number of site visits and the amount of herbicide used.

Technical Abstract: Giant reed is an invasive plant of riparian habitats throughout California and the United States. Two herbicides approved for controlling giant reed in California are glyphosate and imazapyr. Sources indicate that 1.5% to 5% glyphosate solutions are effective at controlling giant reed. Imazapyr has only been recently approved for use in California. There is little published data on the relative efficacy of different concentrations of glyphosate or imazapyr which can be used to select an appropriate application regime for California habitats. We conducted two field experiments and monitored a site where imazapyr had been applied with the purpose of testing two hypotheses relating to these herbicides. One hypothesis was that glyphosate concentrations of 1.5%, 3%, and 5% applied as foliar sprays were equally effective at killing giant reed plants. The second hypothesis was that a 1.5% solution of imazapyr applied as a foliar spray was effective at killing giant reed. Leaf chlorophyll content and the proportion of living stems declined significantly following treatment with 1.5% or greater solutions of glyphosate. New stems were observed the spring following treatment for plants treated with 1.5% glyphosate. No new stems were observed for plants treated with either 3% or 5% glyphosate. There was no evidence indicating that “bending and breaking” stems prior to treatment with 5% glyphosate provided enhanced kill. Nor was there evidence that plants sprayed with only a mixture of the surfactant (agri-dex), water, and a marking dye were affected beyond the short-term. Plants treated with 1.5% imazapyr had reduced leaf chlorophyll content after treatment but recovered the following spring. Imazapyr treatment did not significantly reduce the proportion of living stems or prevent the production of new stems during the spring following treatment. Taken together these results indicate that 3% or 5% foliar applications with glyphosate were the most effective and consistent treatments for killing giant reed with a single late season application. This result is especially important if the goal of the treatment program is to minimize the number of treatments, thus reducing labor costs and minimizing impacts on sensitive habitats by reducing the number of site visits.

Last Modified: 10/1/2014
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