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In: aquatic invasive plants, Biological Invasions, Bret Shaw, Dominique Brossard, Eurasian watermilfoil, fear, herbicide treatments, negative emotions, Richard Heinrich, Theresa Vander Woude, Tim Campbell, University of Wisconsin-Madison

A volunteer looks through a plant rake for invasive species. Monitoring like this is one of the most underrated management actions when invasive species are found in lakes. Image credit: Paul Skawinski

A new study published by University of Wisconsin-Madison researchers is the first to explore what drives lakeshore property owners’ preferences for herbicide treatments of aquatic invasive plants over other management options, even if those treatments may harm native plants and animals. The study found that negative emotions and believing that aquatic invasive species are present in the lake where a property owner lives were the strongest predictors for preferring herbicide treatments. Surprisingly, perceived impacts of aquatic invasive species did not affect preferences for herbicidal treatment of aquatic invasive species.

These results provide an opportunity for natural resource managers to educate lakeshore property owners about alternative methods for managing aquatic invasive plants while still leaving options open for herbicide treatment, if needed.  Other management options include manual and mechanical removal as well as simply monitoring, since non-native plants can often co-exist with other native plants in a lake without taking over and becoming a nuisance.

“People can develop negative emotions about a subject either through lived experiences or through communications about the subject,” said Bret Shaw, lead author and a Division of Extension environmental communications specialist and Department of Life Science Communication professor. “Given that the perceived impact of invasive species is not driving preference for using herbicides, it is possible that fear-based aquatic invasive species prevention messages may influence higher risk perceptions that cause property owners to seek herbicidal treatment first. Considering other approaches and messaging strategies, too, may help lake organizations achieve better outcomes with their management efforts.”

Aquatic invasive plants in Wisconsin lakes can negatively impact recreation and property values. Many organizations offer education and outreach programs for boaters and anglers to prevent invasive species spread.  However, some lakes already have non-native species that can become invasive, and new introductions can occur despite widespread prevention efforts. While there are many ways to manage aquatic invasive plants, lakeshore property owners and lake associations often seek permits to use chemical herbicides even though herbicides themselves can carry a potential risk of ecological harm to the treated lake, which is why herbicides may not necessarily be an appropriate as a first course of action in some waterbodies.

A diver and kayaker remove Eurasian watermilfoil from Spring Lake in Wisconsin. Image credit: Paul Skawinski

Aquatic invasive species are a concern both globally and in Wisconsin, with the Great Lakes on Wisconsin’s borders and another 15,000 inland lakes within them.  While the most problematic invasive species aren’t present in most lakes, where they are located, they can reach high densities that can impede boating, negatively affect fishing and alter the ecological functions of a lake. More than $5 million is spent each year in Wisconsin on aquatic invasive species management. However, even with this annual investment and the negative impacts of aquatic invasive species, very little effort has been spent understanding how waterfront property owners feel and think about invasive species management.

“This research is among the first to understand the opinions and beliefs of waterfront property owners about aquatic invasive species management,” said Tim Campbell, the aquatic invasive species program manager for Wisconsin Sea Grant and co-author of the study. “The results of this research will help us create invasive species management education tools and programs that balance efforts to reduce the unwanted impacts of invasive species while protecting the ecological integrity of our lakes.”

Other co-authors include Dominique Brossard, Professor in the Department of Life Sciences Communication (LSC) as well as recent LSC graduate students, Richard Heinrich (LSC Ph.D. ‘23) and Theresa Vander Woude (LSC and Nelson Institute for Environmental Studies, M.S. ‘21). The full study can be found in the journal Biological Invasions here (https://rdcu.be/dvWb9). Alternatively, email tim.campbell@wisc.edu for a copy.

The post Negative emotions drive preference for herbicide treatments for aquatic invasive species in Wisconsin lakes first appeared on Wisconsin Sea Grant.

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News Releases | Wisconsin Sea Grant

News Releases | Wisconsin Sea Grant

https://www.seagrant.wisc.edu/news/negative-emotions-drive-preference-for-herbicide-treatments-for-aquatic-invasive-species-in-wisconsin-lakes/

Wisconsin Sea Grant

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In: 2 4 D, Eurasian watermilfoil, Gavin Dehnert, herbicides, toxicity to fish

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Wisconsin Sea Grant’s emerging contaminants scientist, Gavin Dehnert, earned his Ph.D. by studying the effects of commercial 2,4-D herbicide exposure on the development and behavior of freshwater fish at different life stages. Now, he’s taking his research out of the lab and into the natural environment, where 2,4-D herbicides are used to treat lakes for the invasive plant, Eurasian watermilfoil.

During his doctoral studies, Dehnert found that exposure to concentrations of 2,4-D similar to those allowed during application to lakes significantly decreased survival in fathead minnow larvae and also other young fish species such as walleye, yellow perch, largemouth bass, northern pike, white crappies and white suckers.

“We saw an increase in about 20 to 35% mortality of the young fish when exposed to 2,4-D,” Dehnert said. “But we kept getting this big question: We know what happens in the laboratory, but what happens in the real world?”

With funding from the Wisconsin Department of Natural Resources, Dehnert designed two sets of experiments this summer in lakes that were undergoing 2,4-D treatments. For the first,

One of two lakewater systems Dehnert uses. In this one, water is taken directly from a lake that had 2,4-D applied, then distributed to tanks where the fish are held. Image credit: Gavin Dehnert, Wisconsin Sea Grant

The second employed an in-lake exposure system. Young fish were put in the lake in two-liter buckets with holes in them covered in mesh, which allowed water and food to pass through, but not the fish.

Dehnert explained, “This allowed us to see what goes on during an actual herbicide treatment. It’s applied to the entire lake and we look at what goes on with the fish.”

He anticipates a possible higher mortality in the lake setting because there are more variables at play. “I would expect more like a 35 to 45% decrease in survivorship because there are more stressors on the fish – temperature changes, storms, nutrient runoff, etcetera. That’s why it’s important to do this experiment in a natural lake setting, so we can get those real-world scenarios,” Dehnert said.

Dehnert is just beginning to process the data from his lake experiments and expects to finish up next year (2022).

Wisconsin lake associations are interested in Dehnert’s work because they want to eradicate Eurasian watermilfoil. Besides the use of an herbicide, the invasive plant can be controlled by manually removing the plants or by introducing beetles that eat it.

“All of these lake associations want to make sure they’re causing the least amount of impact to the other organisms in the lake,” Dehnert said. “So, it’s really exciting to work with them to determine the risks of the different control methods. How do we get rid of this invasive species but keep intact what we already have in the lake?

“Let’s understand what could happen, so we can make an educated decision on whether the benefits outweigh the cons,” he said.

The post Treating lakes for Eurasian watermilfoil with herbicides can harm young fish first appeared on Wisconsin Sea Grant.

Original Article

News Releases | Wisconsin Sea Grant

News Releases | Wisconsin Sea Grant

https://www.seagrant.wisc.edu/news/treating-lakes-for-eurasian-watermilfoil-with-herbicides-can-harm-young-fish/?utm_source=rss&utm_medium=rss&utm_campaign=treating-lakes-for-eurasian-watermilfoil-with-herbicides-can-harm-young-fish

Marie Zhuikov