Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2006
Publication Date: 3/1/2007
Citation: Pokorny, M.L., Mangold, J.M. 2007. Evaluating the success of Montana's Dyer's Woad (Isatis tinctoria) cooperative eradication project. Weed Technology 21:262-269.
Interpretive Summary: Eradication is often stated as an essential element of weed management, yet rarely attempted. Assessing the costs and benefits of eradication programs is often difficult because it requires speculation about the impacts and spread of weeds if eradication measures were not undertaken. The objective of this paper is to describe and assess the Montana Dyer's Woad Cooperative Project, a program aimed at eradicating dyer's woad from Montana. Over the last decade, the Montana Dyer's Woad Cooperative project has successfully eradicated several dyer's woad infestations and largely reduced population sizes at other infestations. Fewer resources have been spent implementing this proactive plan compared to the costs that might have been incurred with widespread invasion and management. We feel the Montana Dyer's Woad Cooperative Project can serve as an example of a successful eradication program upon which weed managers can base similar programs.
Technical Abstract: Eradication is often stated as an essential element of weed management. Assessing the costs and benefits of eradication programs is often difficult because it requires speculation about the impacts and spread of weeds if eradication measures were not undertaken. The objective of this paper is to describe and assess the Montana Dyer's Woad Cooperative Project, a program aimed at eradicating dyer's woad from Montana. The Project is comprised of four key components: early detection, treatment technologies, repeated site visits with monitoring, and education. To evaluate the success of the Montana Dyer's Woad Cooperative Project, we used monitoring data to observe the change in the number of counties where dyer's woad is present, plotted the trend in population size over time, and evaluated change in infestation size. We also predicted population spread based on the 1999 population size and demographic characteristics of dyer's woad. Dyer's woad has been eradicated from nine of thirteen counties infested in Montana and infestation sizes have decreased in the remaining infested counties. In some counties, a containment effort was needed in conjunction with repeated inventories and treatment applications to prevent spread while depleting the seed bank to the point where eradication is possible. If not for the Project, our analysis suggests that some dyer's woad populations may consist of millions of plants, potentially covering 39,021 ha in Montana and costing 1.9 million dollars a year to manage. In comparison, the Project has reduced the total area infested in Montana to 2.6 ha and cost the state only $142,000 for the last seven years of management. In Montana, dyer's woad eradication from individual counties has been successful due to persistence and on-going cooperative efforts.