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Water Management Associations
Aquatic Invasive Species: Hydrilla
Native to Africa and believed to have been introduced to American waters from the aquarium trade in the 1960’s, hydrilla has quickly spread across the southern U.S. from Connecticut to California. By the 1990’s millions was spent yearly on its control, but this year New York alone has budgeted $800,000 to fight the invasive aquatic plant.

Hydrilla forms dense mats of vegetation that interfere with recreation and destroy fish and wildlife habitat. Hydrilla has several advantages over other plants; it will grow with less light, and is more efficient at taking up nutrients than native species. Hydrilla also has extremely effective methods of propagation; it produces seeds and it can also sprout new plants from root fragments or stem fragments. These fragments can be transported to other areas of the lake to produce new plants or hitch rides on boats and trailers to invade other waterways.

Hydrilla is a federally listed noxious weed and in accordance with the Federal Noxious Weed Act of 1974 the movement of the weeds in interstate or foreign commerce is prohibited except under permit. Authority is also given to inspect, seize and destroy products, and to quarantine areas, if necessary to prevent the spread of such weeds.

Biological, Chemical, Manual, and Mechanical Control have all been used to manage hydrilla. Each control method has advantage and disadvantages and often times combined methods are successful.

Biological Control
Grass carp, an herbivorous fish with a ferocious appetite has been proven effective to help control hydrilla. Unfortunately, the fish does not eat only hydrilla and also will consume most submersed and emersed aquatic plants once hydrilla is depleted.

• Chemical Control
Herbicides offer an effective control for hydrilla and are often fast acting. Regulated by the EPA and applied by certified applicators it has been deemed a safe option for control. One danger with any chemical control method is the chance of oxygen depletion after the treatment caused by the decomposition of the dead plant material. Plants can also become resistant to herbicides which then requires the use of a new a chemical.

• Physical Control
Physical control includes a number of techniques such as hand pulling, draw downs, and aeration. While all are somewhat effective, they are labor intensive and expensive.

• Mechanical Control
Mechanical control cuts and collects the hydrilla for on shore disposal and offers and environmentally friendly option with immediate results. While effective in managing hydrilla and removing the plant material to prevent them from decaying and adding additional nutrients to the water; aquatic weed harvesters require a capital investment and needs to be done more than once a season.

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Osoyoos Mayor in a War Over Weeds with U.S. - The (American) Okanogan County Noxious Weed Control Board has applied to a national environmental agency to treat Eurasian water milfoil with an aquatic herbicide, much to the dismay of the (Canadian) Okanagan Basin Water Board.

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