Inventive Resources, Inc.

Weed Control PROJECT

Tahoe AIS

An Innovative Approach to Eradicate Nuisance Plants

Why are aquatic invasive plants like Eurasian watermilfoil a concern to our water bodies?  What are some options to treat and prevent Aquatic Invasive Plants?

Invasive aquatic plants — it doesn’t sound concerning does it? But these invaders have devastating effects on U.S. wildlife and waterways.  Invasive species are one of the leading threats to native wildlife.  Approximately 42% of threatened or endangered plants and wildlife are at risk primarily due to invasive species.  Human health and our economies are also at risk, the impacts of invasive species on our ecosystems and economy cost billions of dollars each year.  Commercial and recreational activities depend on healthy waterways.  If water ways are aesthetically and biologically undesirable, than in the short term, visitors will seek other areas for recreational activities causing other indirect commercial businesses to suffer as well.  In the long term, the cities and towns that host these water bodies will suffer economically.  In most cases, property values decrease and commercial businesses suffer economically.


UV treatment underway at Lake Tahoe (Photo courtesy of


Attempts to control or locally eradicate aquatic invasive plants (AIP), specifically Eurasian watermilfoil (EWM), have been on-going in water bodies all across the United States.  Herbicides, gas-permeable bottom or benthic barriers, diver assisted suction removal and harvesting have been a few of the methods entities have used to remove AIP from water bodies.

Eurasian watermilfoil is native to Europe, Asia, and northern Africa. As of 2003, 45 states reported the presence of Eurasian watermilfoil.   This invasive species is of growing concern because its ease to spread by root and by broken segments.    If Eurasian water milfoil is left unabated it can easily take control of a water way and deplete a water body of its native life.  It can also make recreational activities unpalatable if not impossible to partake, it can clog boat motors, pipes, water intake screens.  This type of plant can easily wrap around boat rudders and cause damage to boats.  Fish and birds can also become tangled in these plants.  Invasive plants can deplete water from dissolved oxygen levels making waters unsuitable for fish to live.  

Eurasian water-milfoil negatively affects the water bodies it invades in several ways:  

  1.  Due to its tendency to branch profusely and form a dense canopy over the water surface, it will shade out the native vegetation.  This can alter the species composition of the water which can result in a near monoculture of Eurasian watermilfoil. 
  2. This plant is not a valuable food source for waterfowl unlike some of the native submersed aquatic plants.
  3. Plant biomass can become so dense that predator fish will lose their foraging space and will be less effective at controlling prey species resulting in an imbalanced fish community.
  4. Dense beds of Eurasian watermilfoil make recreational activities such as boating, fishing and swimming nearly impossible.   Residents that have had to deal with this plant in their areas have also noticed that the dense living environments of this plant make it very hard for any boat they made have for example fishing, this is because the watermilfoil get tied up with in the rudders of the motor and cause an extreme hassel, sometimes even destroying the motor.
  5. Residential or industrial water intakes can become clogged with Eurasian water-milfoil.
  6. Dense plant beds can be nursery areas for mosquito larvae.
  7. A lake heavily infested with Eurasian watermilfoil will be aesthetically displeasing which results in reduced property values.
  8. In 1998, 160 permits were issued for herbicide treatments on public waters in Indiana.  Approximately four of every five permits issued targeted Eurasian watermilfoil. A conservative estimate of the cost of controlling exotic plants that interfere with recreation and drinking water supplies in Indiana is in the neighborhood of $1.2 million per year.  

What are local agencies doing to controlling and ultimately stopping such infestations to our waterbodies?  

Once AIP become established and spread, it can be extraordinarily difficult and costly to control or eradicate them. As a result, the best approach for dealing with the invasive species is to:

  1. Create effective mechanisms to prevent their introduction in the first place,
  2. Create monitoring systems for detecting new infestations,
  3. Move rapidly to eradicate newly detected invaders using a combination of methods,
  4. Educate the public on how to avoid and to alert the public agencies of any visible infestations.

Item 3 and 4 are very important in management of these nuisance plants.  Once an infestation is located, it is imperative to seal the area and prevent plant breakage or drift to other areas by boaters.  Currently there are only a few ways to control Eurasian water milfoil.  These methods include:

  1. Mechanical Harvesting
  2. Herbicide Treatment
  3. Gas Permeable Bottom Mat Barriers
  4. Diver assisted suction

Unfortunately due to the biology of some invasive aquatic plants, specifically Eurasian watermilfoil, mechanical harvesting can cause greater infestations if the segments aren’t fully captured if operation methods are not performed properly.  A mechanical harvester is essentially pulling plants out of the water, at times breaking them in segments; causing the potential for fragments to sprout new plants, which leads to greater infestation.  Mechanical harvesters are labor intensive and require regular scheduled maintenance and complete segment capture in order to see positive results.  Harvesters do not necessarily eradicate invasive plants, merely clip and roll them.

Herbicide use for treating infestations has started to become more popular in extreme cases of infestations.  Even certain agencies around the United States have started to approve certain herbicide uses.  The use of herbicides has been highly controversial especially in water bodies that are used for their domestic water supply and have high contact with people. Herbicides are designed to treat an entire areas and do not discriminate on whether it’s a native or nonnative plants. Herbicide use are the least labor intensive, although regulators have deemed herbicides safe for use in water with specific treatment parameters.  However, many people are skeptical on the safety of herbicide use and it is unknown the long term affects it can cause to fish, humans or local water supply. 

The use of gas permeable bottom barriers and diver assisted suction removal is also used in some cases.  This method is labor intensive, as these barriers need to be removed seasonally.   Wave action, lake-bottom morphology, high boater use areas, and turbidity can impede the effectiveness of any of these methods. While a combination of methodology has been successful in an open water setting, limitations do exist and no one way is a perfect solution to this growing problem.   We need other options to treat these types of infestations.  Inventive Resources Inc (IRI) has developed a treatment method that uses ultraviolet light to damage and kill invasive aquatic plants.  We feel that our patented UVC treatment apparatus is the ideal tool to fill a desperate need to combat aquatic invasive plants.  


Left side of marina was treated approximately one week before photo was taken. All plants on the treated side have collapsed. (Photo courtesy of


New research indicates that ultraviolet-C (UVC) light, a short-wave electromagnetic radiation light that damages the DNA and cellular structure of aquatic plants and their fragments could be an effective new method.  We are currently running a Pilot Study using this technology in lake water.  This project will utilize two lake environments: open water and enclosed water (marina), to test the effectiveness of UVC light technology for the treatment of aquatic invasive plant infestations. The technology has shown success following laboratory testing where results indicated complete mortality of plants and fragments treated with UVC light under various water temperatures and depths, and with different plant types, sizes, and age classes. Laboratory testing revealed treatment exposures of 5 - 60 minutes resulted in complete elimination of tested plants.  It is anticipated that results in the field will have a similar impact. 

If you would like to discuss if this type of treatment is ideal in your area, please send us your contact information in the section below.  Our engineers would be happy to discuss this process with you.

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