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Invasive species


Mayme Keagy


When non-native species are introduced into a new area the species can take over and spread rapidly and widely throughout the area. When this happens, the spread can cause major harm to the native ecosystem or humans. When non-native plants, animals or pathogens rapidly take over a new location and alter the ecosystem, we consider them invasive species.

One of the reasons that invasive species are able to succeed is that they often leave their predators and competitors behind in their native ecosystems. Without these natural checks and balances, they are able to reproduce rapidly and out-compete native species.


Invasive species are considered to be the number two threat to biodiversity, second only to habitat loss. The effects of invasive species are increasingly evident on Wisconsin’s landscape. Despite efforts by federal and state agencies, non-native insects, plants and diseases continue to establish and spread throughout our state, impacting our economy and environment. While some of these pests are here to stay, many others have not yet been found in Wisconsin, and still more are found at low enough levels that eradication may be possible. Efforts to prevent new introductions and to identify new infestations before they become well established are the best way to ensure the survival of many of Wisconsin’s iconic plants, animals, and ecosystems.


The Wisconsin First Detector Network (WIFDN) is a citizen science network that empowers people to take action against invasive species through invasive species monitoring, management, and outreach. Use the UW Online Weed Key to help identify invasive plants or visit this story map to access species distribution maps, additional I.D. information, and priority species in your county.


Wisconsin First Detector Network


Suggested mowing and treatment times for weeds in Southern Wisconsin.

Mowing can be an effective control for some invasive species; however, it can spread those species if not timed correctly. Mowing can be done multiple times per growing season. Avoid mowing if seeds have already developed as this will spread them.


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Mowing timetable to suppress weeds


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Treatment timetable to suppress weeds


Reed Canary Grass Management Guide: Recommendations for Landowners and Restoration Professionals


This guide walks you through the steps you can take to manage reed canary grass. It provides a summary of treatment options that can be used. Helps you conduct a site assessment and decide which techniques are best suited to your budget and situation, and lists native species that may provide competition for reed canary grass during restoration and management efforts.

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Canary Reed Grass Management

Fact-sheets for common invasives in Southwest WI

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Common Buckthorn

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Bush Honeysuckle

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Canada thistle

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Multiflora Rose

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Wild parsnip

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Garlic mustard

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