Lake Ouachita Vegetation Control

Lake Ouachita vegetation is being addressed by the U.S. Army Corps of Engineers, Arkansas Game and Fish Commission, and the Lake Ouachita Association to control Hydrilla and Eurasian Watermilfoil.

“The goal of the project is to contain and reduce the vegetation, not eradication, since the presence of aquatic vegetation in moderate amounts is beneficial to the lake’s fishery,” Wooldridge said.

Satellite imagery by the U.S. Army Corps of Engineers shows the lake contains 10,000 acres of vegetation, according to Richard Stokes, Lake Ouachita project manager. The goal of the project is to reduce the coverage by 2,000 acres. We will concentrate on high recreational use areas, such as swimming beaches, around marinas and popular boating areas. Areas of the lake containing good fishery habitat will not be treated, Stokes added.

The C.O.E. is treating 13 areas with Pakistani flies a tiny fly that resembles a gnat in size and hops along the water surface rather than flying. The Corps of Engineers will inoculate 13 selected areas of Lake Ouachita with the fly , whose larvae feed exclusively on hydrilla. The Larvae of the fly will kill the upper three feet of the plants. The Pakistani hydrilla leaf-mining fly’s larvae (hydrellia pakistanae) burrow into the leaves of the plant. Each larva can destroy nine to 12 leaves during its feeding cycle.
The flies will take several years to become noticeably effective.

Other Biological Control of Invasive Species.

Lake Ouachita Weed Identification

Hydrilla Verticellata Description:

Hydrilla Verticellata, commonly referred to as Hydrilla is a very invasive submersed freshwater herb.

It was originally sold as an aquarium plant. It forms very dense strands growing from the bottom of the water and sprawling across the surface.

Although it is an excellent source of food for waterfowl, it can be a serious threat to freshwater habitats and a nuisance to boaters.

Hydrilla reproduces by fragmentation.
It does not form any seeds.

Even small pieces stuck on boat propellers or in bait pails contribute to the easy spread of Hydrilla to other areas and waterways.

Will grow in 30 feet of water.

Hydrilla produces large strands of plants in just a few months through its efficient use of low light levels and available nutrients.

Hydrilla Identification:

Green, freshwater herb

Submersed plant with long slender stems

2 to 8 small, spear-like leaves per whorl spread across the water

The leaf has a sawtooth edge and small spines on the underside that are rough to the touch

Grows in as little as a few inches of water or in more than 30 feet of water.

Milfoil Description:

Eurasian Watermilfoil (Myriophyllum Spicatum) is native to Europe, Asia and northern Africa. It was introduced to the United States many years ago in the 1940’s.

Eurasian Milfoil is an underwater plant and bears only a slight difference from US native Milfoil. Because it is an attractive plant, it was once commonly sold as an aquarium plant.

The Eurasian Milfoil has 12-21 pairs of leaflets leaf and the native northern Milfoil only has 7-11 pairs of leaflets

Milfoil grows best in fertile, inorganic sediments. It prefers very active lake beds which receive nitrogen and phosphorous-laden runoff. Because of the poor seed germination, it reproduces by fragmentation.

It produces fragments during the summer after fruiting once or twice. The shoots get carried away by currents or boaters. Because of its ability to spread rapidly, it often blocks out sunlight for plants native to the lakes. The dense groups can also block out larger fish, therefore disrupting the predator-prey relationship. Many waterways become congested due to these dense groups as well.

Milfoil Identification:

Reddish-brown plant stem that thickens below the water and curves to lie parallel with the water surface

Submersed feathery leaves

Tiny 4 part flowers stick out 2 -4 inches above the water

The flowers can be four petaled or without any petals

The fruit is contained in a hard capsule with 4 seeds in it.

Coontail The Desirable Plant Description:

Coontail (Ceratophyllum demersum) is a free-floating submersed plant without any roots.

Coontail is desirable when managing for waterfowl and fisheries. The leaves and seeds of coontail are eaten by waterfowl, and it provides a home for a variety of aquatic insects.

These insects then serve as food for many species of fish and waterfowl.

Coontail also provides cover for small fish, which is important in relatively clear lakes.

Coontail draws its nutrients from the water directly rather than from sediment like most rooted aquatic plants.

It can survive in cool waters and low light. During the winter months, it can live under the ice as an evergreen plant and resumes rapid growth in the spring.

Coontail Identification:

Dark green forking leaves, up to 1 2 inches in length arranged in whorls on the stem

Submersed plant without roots

Plants may be bushy or very long and sparse

Feathery leaves on the stem resemble a raccoons tail. The stems can be 1 to 2 feet in length.

The leaf has small teeth on the midribs which make it rough to the touch

It has very small flowers which are rarely seen