March 15, 2019

March Weed of the Month: Knotweed Survey

Mari Hardel, Minnesota Department of Agriculture

In 2018, the Minnesota Department of Agriculture’s (MDA) Noxious Weed Advisory Committee (NWAC) revisited the risk assessment of non-native invasive knotweeds and developed a survey to gather information from the public. Knotweeds typically grow in residential areas – often planted in landscapes – and therefore affect a different group of people and settings than most species on Minnesota’s Noxious Weed List. In surveying the public, the NWAC hoped to gain insight on perception and knowledge of knotweeds in Minnesota and potential responses to a change in regulation of knotweeds. This past September, an online survey was created and distributed to both the public and land managers asking a variety of questions related to non-native invasive knotweeds in Minnesota, beginning with whether survey participants were familiar with the three invasive species present in Minnesota and surrounding area: Japanese, giant, and Bohemian knotweeds. If participants claimed to have a low level of knowledge on knotweeds, they could choose to opt out of completing the bulk of the survey and skip to the end, answering general questions about where they obtain information on plants. Participants who completed the entirety of the survey were tasked with identifying photos of knotweed and knotweed look-alikes, answering questions about perceptions of knotweed and management techniques, and describing resource desires regarding managing knotweed.

The survey was distributed through the MDA’s September Weed of the Month article titled Knotweeds, various newsletters and social media pages, handouts at Duluth’s Western Lake Superior Sanitary District, via email to MDA stakeholder groups, and additional avenues.

Complete survey results are available on the MDA Noxious and Invasive Weed Program page. Survey results were also presented in a poster format at the Upper Midwest Invasive Species Conference in Rochester, Minnesota from October 15-18, 2018.

The following are some highlights from the survey data:

• 211 people responded to the survey. Participants responded from across the state, with the Duluth area the best represented.
• In general, respondents had some knowledge of knotweeds (Japanese, giant, and Bohemian): 16% were familiar with all three species of knotweed; 33% were not familiar with any; 38% were familiar with Japanese ONLY; and fewer were familiar with Bohemian and giant knotweeds.
• More people correctly identified knotweed when viewing a photo containing knotweed stems (and leaves) than any other features of knotweed.
• Most felt that there are NOT sufficient resources for managing non-native invasive knotweeds.
• Eight out of ten respondents agreed that knotweeds should be regulated in Minnesota.

After reviewing survey results, in addition to considering research and other sources of information, the NWAC recommended regulation of knotweeds as ‘Prohibited-Control’ on the Minnesota Noxious Weed List. This is a change from the current status from ‘Specially Regulated’. The Commissioner of Agriculture approved this recommendation and the change will become effective January 1, 2020.

PHOTO

Click here to download the image.

Caption: A flowering Japanese knotweed stand in Duluth, Minn.

MEDIA: For more information on Weed of the Month, contact Allen Sommerfeld, MDA Communications, at allen.sommerfeld@state.mn.us or 651-201-6185

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