According to the Corps, the densely packed flowering rush can “degrade water quality (including impacts on irrigation and potable water), decrease aquatic biodiversity, negatively impact fish and wildlife habitat (including bull trout), harbor swimmers itch and interfere with shoreline activities.”

Herbicides are used both in conjunction with — and as an alternative to — physical control methods; however, they have the potential to harm native plant species growing in or near the application sites. Additionally, the leftover decomposing plant matter draws oxygen from the water, which can harm nearby fish.

There were no fishing or swimming restrictions in place at the treatment sites, however, locals were advised to wait three days before drinking the water or irrigating their landscapes, and five days before watering their crops, according to the Corps’ treatment notice.

Lake Pend Oreille in the northern Idaho Panhandle is the largest lake in the U.S. state of Idaho and the 38th-largest lake by area in the United States.

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The reason, according to the commission: The project would not “significantly improve the capacity of the Stockbridge Bowl to protect and sustain” the ecological restoration of the lake under the state’s Wetlands Protection Act.

In a separate decision, the commission also rejected the project under the town’s wetlands bylaw, voting unanimously that the treatment approved by state and federal environmental agencies would “harm the environmental quality of the Bowl,” or “would have unacceptable significant or cumulative effects upon the resource area values protected by the bylaw.”

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But maintaining that beauty, and more importantly, what’s under the water, can be challenging and at times controversial.

Lake Shawnee is one such area where Eurasian watermilfoil has flourished, leading the county to use herbicides in recent years to combat the spread of the weed.

One opponent of the herbicide use believes the introduction of herbicides to Lake Shawnee in past years has been detrimental to the bass population, and said mechanical or manual removal of excess weeds would be a better option. He also said that watermilfoil helps increase fish populations in lakes, and that some of his best fishing experiences have been at lakes where the plant grows.

Read More  https://www.cjonline.com/story/news/state/2019/08/17/lake-shawnees-use-of-herbicide-to-combat-eurasian-milfoil-draws-criticism/4437712007/

About 400 fish, including largemouth bass, died last week in Libertyville Illinois’s Butler Lake soon after a company applied a chemical that’s designed to control invasive weeds, including the lake’s excessive growth of water lilies.

Libertyville public works director Paul Kendzior tells The Daily Herald that the vegetation die-off caused dissolved oxygen levels to fall, depriving fish of oxygen and killing them. He says the herbicide application itself didn’t directly harm the fish.

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Overall, the research showed year-to-year variability in the total biomass of starry stonewort. There were good years and bad years for it. Warm summers adversely affected its total biomass, while warmer winters appear to have allowed it it to expand its coverage area, according to the research.

While warmer summer temperatures could reduce the total biomass, the area of a lake bottom covered by starry stonewort tended to increase in the summers that followed warmer winters. In this way, water winter temperatures could be associated with greater spread of starry stonewort.

Much more needs to be learned, but the data can help find the most effective methods for controlling the invasive plant. In many of the infected lakes, Koronis included, mechanical harvesting and herbicide applications are being used to manage it.

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Hydrilla, which is native to Africa, Australia, and parts of Asia, forms dense mats of vegetation that interfere with recreation and destroy fish and wildlife habitat.  This plant is able to survive freezing temperatures and can grow in very low sunlight which is a huge advantage over native aquatic plants.  Hydrilla grows early in the season and quickly shoots to the water’s surface blocking the sunlight and absorbing nutrients native plants need to survive.

No lake is immune since a fragment of the plant, often transported from lake to lake via boats, is capable of regenerating new plants.  Lake Pinehurst, a 200-acre manmade lake is owned by Pinehurst Resort in North Carolina; a premiere golf and recreation resort. Power boats are not permitted making it an ideal lake to host cocktail cruises, sail, swim, and fish.  Well, maybe not fish – not anymore.  Residents and resort guests trolled for largemouth bass and other fish that were once plentiful in the lake.  Pinehurst Resort advertised a well-stocked lake and provided fishing guide services for guests.  That is until hydrilla was discovered, Pinehurst Resort and members of the homeowners association quickly ordered herbicide spraying to combat the aquatic invasive species.

Aquatic vegetation had always been a problem in shallow parts of the lake and years of limited spraying kept the vegetation under control.  Three years ago an intensive annual program of spraying herbicides to kill the hydrilla began.  The program costs $20,000 annually and has proved to be successful, at least if near complete obliteration of plant life was the goal.  Very little aquatic vegetation remained after the spraying program, and native vegetation is necessary to keep lakes healthy, filter pollutants, and create fish habitat.  The annihilation of the aquatic vegetation has led to an unproductive fishery in poor shape; there is lack of forage fish which has resulted in stunted and unhealthy game fish.

According to the North Carolina Agricultural Extension Service, heavy hydrilla infestations (those that cover more than 25 to 30 percent of the surface in a lake) eliminate fish habitat, cause stunting, and reduce the number of harvestable fish.  Also, low oxygen levels under the mats make them unsuitable for the growth and survival of sport fishes and most other aquatic animals.  It’s interesting to note that the results from the treatment plan sounds hauntingly familiar to a hydrilla infestation.  Of course the hydrilla is gone now.

At the urging of fishermen in 2011, a study was conducted by Foster Lake & Pond Management, to include an analysis of the health of the current fish population in the lake, analysis of the food chain, survey of the lake’s bottom, study of aquatic plants, water quality and the negative effects of the lake’s population of grass carp.  The report concluded that the aquatic vegetation proved to be bladderwort, a carnivorous plant that is native to North Carolina; no hydrilla was found actively growing, but that tubers from the weed could be present in the hydro soil.  The grass carp were found to be healthy and actively feeding on what little aquatic vegetation remained.  The main problem in the lake now is a shortage of forage fish, those upon which the game fish feed; resulting in stunted and unhealthy game fish.

Recommendations were made on how to help fix the problem that the herbicide treatment caused.  These included harvesting certain fish, forage fish restocking, a feeding program and habitat enhancement.  In an effort to add habitat, discarded Christmas trees were submerged as a type of artificial habitat.

So although there is not funding to aid the “unproductive fishery that is in poor shape” there is money to continue with chemical treatments.  A small group of sportsmen and homeowners are hoping to find a way to compromise with those who find any aquatic vegetation a nuisance.  Aquatic vegetation can be controlled without killing all of the aquatic vegetation which is necessary to keep Lake Pinehurst healthy; it is a lake after all and not a 200-acre chemically treated pool.