Aquatic Vegetation Management


What is an aquatic weed?

Aquatic plants are an important component of freshwater ecosystems and perform a wide variety of beneficial functions.  Under certain conditions, however, aquatic vegetation can become a nuisance and disturb the ecological balance.  When a plant interferes with the beneficial use of a water body it is recognised as an aquatic weed.

Apart from plants (macrophytes), the overabundant growth of algae and blue-green bacteria (cyanobacteria) may also interfere with the beneficial uses of an affected water body.

Kinds of aquatic vegetation

Submerged Aquatic Vegetation

Submerged or submersed plants are plants that grow almost entirely under the surface of the water, although they do have the potential to reach the surface. The prolific underwater vegetation commonly known as pondweed, which include Potamogeton and Lagarosiphon species can put a stop to boating, fishing and irrigation.  Submerged vegetation is also a big problem in trout and bass dams.

Submerged Aquatic Vegetation

Floating Aquatic Vegetation

Floating plants are those plants that are vascular and do have roots, but their roots are not necessarily established in the bottom sediment. Floating plants like water hyacinth (Eichhornia crassipes), Kariba weed (Salvinia molesta), water lettuce (Pistia stratiotes), duck weed (Lemna gibba), red water fern (Azolla sp.), Spirodella sp. and Wolffia sp. can accelerate siltation, water loss, suppress indigenous species and may ultimately destroy an aquatic ecosystem.

Floating Aquatic Vegetation
Peripheral (emergent) Aquatic Vegetation

Reeds, such as giant reed (Arundo donax), Phragmites and bulrush (Typha sp.) can impede flow and greatly increase water loss due to evapo-transpiration. They increase the danger of flooding, and decrease capacity and accessibility to water bodies. Only herbicide treatment is effective against reed growth.

Peripheral (emergent) Aquatic Vegetation

Algae and blue-green bacteria

Algae such as Cladophora, Oedogonium, Vaucheria and many others, give rise to enormous operational problems in irrigation canals and urban impoundments throughout Southern Africa.  Filamentous algae are especially responsible for water losses from canals and the blockage of filters.  Blue-green bacteria (eg. Microcystis, Anabaena, Oscillatoria and others) microtoxins can be toxic to man and lethal to livestock, producing aesthetically unpleasant odours and tastes, and reducing shoreline property values at eutrophic (nutrient enriched) reservoirs.

Algae and blue-green bacteria

Are aquatic vegetation and algae taking over your lake?
A water body is a complicated ecosystem which needs ongoing maintenance and restoration. When problem plant populations limit the uses of a water body, the solution lies in careful management to rehabilitate the problem. Finding a remedy to nuisance aquatic vegetation that is effective, ecologically sensitive, and economically feasible is the goal of an Integrated Aquatic Vegetation Management Plan.

ENVIROKONSULT™ is your answer to your aquatic vegetation problem…
Designing a cost-effective and environmentally sound Integrated Aquatic Vegetation Management Plan (IAVMP), necessitates a knowledge of the history and current condition and ecological status of the affected water body, the uses thereof, as well as the possible control methods that may be applicable to the specific water bodies circumstances. Control methods can vary widely in cost effectiveness and environmental impacts. ENVIROKONSULT™ scientists and technicians are well trained and fully licensed herbicide applicators with the ability to address small and large scale aquatic vegetation problems in all water bodies.

ENVIROKONSULT™ makes use of a range of aquatic vegetation control methods
Herbicidal (chemical) control:
This control method implies the application of registered herbicides and algaecides according to conditions stipulated in the Agricultural Remedies Act (Act Nr. 36 of 1947).

Mechanical/physical control:
Mechanical control of macrophytes and algae is only effective on a small, site-specific scale. This control method involves the application of machinery such as weed harvesters.

Biological control:
Biological control is a longer-term solution and is usually target specific. In biological control programmes insects, other invertebrates and pathogens (fungi and bacteria) are used to control aquatic weed proliferation. ENVIROKONSULT™ also uses herbivorous fish (Sterile Grass Carp) to effectively control aquatic vegetation in dams and irrigation canal systems.

Integrated control:
An integrated control strategy incorporates a combination of two or more of the above-mentioned control methods into an effective Integrated Aquatic Vegetation Management Plan (IAVMP). When combining different control methods, the IAVMP aims to optimise the chosen methods for maximum target specificity and minimum environmental impact.