MAYVILLE — A white paper released Tuesday makes clear that Chautauqua County needs to have a coordinated yearly plan to deal with invasive weeds in Chautauqua Lake.

Ecology and Environment Inc. recently provided Chautauqua County with “Summary of Methods for Control of Aquatic Invasive and Nuisance Plants with Special Emphasis on Eurasian Watermilfoil and Curly-leaf Pondweed.” The white paper has an emphasis on the available herbicides that could be used in New York state and examines various biological, chemical and physical aquatic plant management techniques to help control the amount of Eurasian watermilfoil and curly-leaf pondweed, the lake’s two most problematic plant species. It also identifies the advantages, disadvantages, and environmental impacts associated with each technique from a third party perspective.

“We were pleased to have this independent, third party firm evaluate various approaches to address the weeds in Chautauqua Lake,” said Mark Geise, deputy county executive for economic development. “It is important that we have an approach to periodically evaluate our decisions and goals for Chautauqua Lake, and E&E’s white paper will help us establish best management practices for our Comprehensive Lake Management Strategy.”

The report makes clear that a balanced approach is needed to control nuisance invasive weeds in the lake. Mechanical cutting and harvesting needs to be repeated more than once per year and can balance habitat, recreational and other public use needs. The white paper also states that depending on the method, that aquatic plant species like Eurasian milfoil that grow rapidly and regenerate from fragments have a competitive advantage under a harvesting regime, though with proper timing harvesting can be effective at controlling regrowth of curly-leaf pondweed.

Dredging can be an effective way to control sediment-bound nutrients and vegetation but is non-selective and removes all plants, including non-invasive vegetation. Water level control can also help, the white paper states, because lowering the lake level over the winter allows exposed sediments to freeze, causing the greatest impacts to submerged species. Lowering water levels has been found to effectively control milfoil species and enhance pondweed species.

Some of the physical management techniques that have or could be pursued are mechanical harvesting, hydroraking, hand harvesting, dredging, and water level control. Biological techniques that have or could be implemented are the introduction of fish, insects, or pathogens that will impact the targeted plant species.

The report also discusses nine herbicides registered in New York state for use on submerged aquatic vegetation, including copper, diquat, endothall, florpyrauxifen-benzyl, flumioxazin, fluridone, imazamox, triclopyr, and 2,4-dichlorophenoxyacetic (2,4-D). Ecology and Environment officials conclude that a rotation of selective herbicides, used systemically, will lead to the fewest impact on non-target weeds and effectively control Eurasian milfoil. Systemic herbicides aren’t as effective on curly-leaf pondweed, so spot treatments are recommended even though there will be some impacts to native pondweeds.

“E&E brought a very balanced perspective to their analysis,” said Pierre Chagnon, Chautauqua Lake and Watershed Management Alliance chairman. “They observed that aquatic plant management tools and techniques are classified as physical, chemical, or biological. All of these tools and techniques come with advantages and disadvantages and have environmental impact. Management approaches should be selected based upon waterbody-specific economic, environmental, and technical constraints, and should fit the site-specific management goals.”

The report calls for an integrated pest management technique that doesn’t rely on one single tool to control nuisance invasive weeds. Such an approach includes a combination of physical, chemical and biological methods, such as herbicides or mechanical harvesting, hand-harvesting or benthic barriers, preventative measures like boat launch stewards to prevent invasive species from reaching the lake in the first place because, “no one management tool or technique is sufficient for all scenarios,” the report states.

The report states that it is inefficient to stock a lake with herbivorous organisms to control weeds or to use mechanical harvesting as a primary method of management because the methods defeat each other. Conversely, relying only on herbicides leads the invasive species to begin resisting the herbicides.

“E&E found that herbicides can be a selective and effective management technique against Eurasian watermilfoil and curly-leaf pondweed,” said County Executive George Borrello. “However, as identified in the report, it is important that herbicides are not the only tool in our toolbox to restore Chautauqua Lake. We need to make sure we are using other non-chemical techniques in conjunction with herbicides in order to effectively control invasive weeds while having minimum impact on non-targeted species.”