Just like the 1958 science fiction classic movie “The Blob”, Giant Salvinia burst onto the scene in the United States, becoming one of the world’s worst invasive aquatic plants. In 1998 Giant Salvinia was recognized as a U.S. problem when eradication was resisted near Houston, Texas. Giant Salvinia has an “explosive” growth rate and can easily double in size in just a few days.
Native to Southern Brazil, Giant Salvinia is now found in India, South East Asia, Africa, New Guinea, Australia, Indonesia, Philippines, New Zealand and a host of other countries including the United States.
Biologists believe Giant Salvinia was introduced by the aquarium and garden pond industry, which probably distributed it as an ornamental, not knowing of its invasive potential.
Giant Salvinia is a free-floating fern with small elliptical leaves, green to brownish-green in color. Upper leaves are covered with rows of white bristly hairs. It reproduces new branches developed from lateral buds and through vegetative fragmentation. These dense mats form rapidly and are distributed quite easily by wind and wave action.
This rapid growth can severely reduce oxygen supply into the water. This decrease of oxygen can be stressful and even detrimental to fish and other aquatic organisms. This reduction in aquatic life will severely impact the area for waterfowl. Giant Salvinia also provides an ideal habitat for mosquitoes that can transport disease such as encephalitis and West Nile Virus. It clogs waterways, preventing boating, waterskiing and fishing. Finally, it can have a devastating impact on crop production that use irrigation systems.
At this time, an effective way to control the spread is through herbicide use. Herbicidal control produces control in as little as two weeks. Small-scale outdoor studies have shown diquat, copper, and fluridone are all effective against this weed. It has been noted that young plants are more responsive to most herbicidal techniques that have been tried.
The C. salviniae aquatic weevil, native to Brazil, has also been used successfully for biological control. Adults consume leaves and buds, inhibiting new growth. This helpful weevil has been used successfully in more than 13 countries over 3 continents.
The most effective control of Giant Salvinia and any other invasive aquatic plant is prevention.