Salvinia molesta

S. molesta is a complex of closely related floating ferns and can be difficult to distinguish from each other. This water fern is often grown as an ornamental plant but has escaped and become a noxious pest in many regions worldwide. There are a few different growth forms for S. molesta; the primary growth form is an invading form with small flat leaves, while the tertiary or mat form has large, crowded, folded leaves. Under the best conditions, plants can form a 2-foot-thick mat. These mats can put a halt to recreational activities on lakes and waterways. S. molesta has been used to extract nutrients and pollutants from the water. When this plant is dried out, it can be used as mulch. The phenolic compounds 6'-O-(3,4-dihydroxy benzoyl)-beta-D-glucopyranosyl ester, 4-O-beta-d-glucopyranoside-3-hydroxy methyl benzoate, methyl benzoate, hypogallic acid, caffeic acid, paeoniflorin, and pikuroside can be isolated from S. molesta.{{Cite journal ==Growing conditions==

S. molesta reproduces only by asexual reproduction, but it is capable of growing extremely quickly, starting from small fragments and doubling in dry weight every 2.2–2.5 days. It grows from fragments that have broken off or dormant buds that have been detached from the main plant. Each node has 5 buds, so the potential for rapid spread is high. It also produces spores that are genetically defective and do not produce viable offspring. S. molesta prefers to grow in slow-moving waters such as those found in lakes, ponds, oxbow lakes, streams, ditches, marshes, and rivers. It prefers nutrient-rich waters such as those found in eutrophic water or those polluted by wastewater. It does not usually grow in brackish or salty waters, but has been reported in streams with a tidal flow in southeast Texas. It handles well with dewatering, and while it prefers to grow in moderate temperatures, it will tolerate low or very high temperatures. The United States Geological Service believes that it could grow in zones 7a, 8, 9, and 10 of the USDA Plant Hardiness Map. ==Distribution==

S. molesta is native to Brazil, but is now widely distributed in tropical and subtropical areas. This floating fern is known for its capability to take over large bodies of slow-moving fresh water. S. molesta has been naturalized in Texas and Louisiana, but has now also been found and reported in Alabama, Mississippi, Florida, and Georgia. It can also be found where the lower Colorado River borders Arizona and California. "While S. molesta rapidly colonizes new states, current populations are too small to assess, but have been targeted for eradication". The naturalized regions of Texas have 14 drainage basins that contain infested water bodies; these are used as impoundments on tributaries that flow near federally protected wetlands. In October 2020, Texas Parks and Wildlife detected S. molesta on Lone Star Lake while surveying fish populations. ==Relation to humans==

Salvinia effect The salvinia effect describes the stabilization of an air layer upon a submerged hydrophobic (water repellent) surface by hydrophilic (water-loving) pins. This physico-chemical phenomenon was discovered on the floating fern S. molesta by botanist Wilhelm Barthlott (Universität Bonn) while working on the lotus effect and was described in cooperation with physicist Thomas Schimmel (Karlsruhe Institute of Technology), fluid mechanist Alfred Leder (Universität Rostock), and their colleagues in 2010. Bioremediation Research done in the Philippines suggested the effectiveness of S. molesta for the treatment of blackwater effluent for an eco-friendly sewage system that uses a constructed wetland to clean the water. The result of the study showed that it can remove 30.77% of total suspended solids, 74.70% dissolved oxygen, and 48.95% fecal coliform from the water. Cancer research Researchers at Stephen F. Austin State University in Nacogdoches, Texas, discovered that extracts of giant salvinia have shown promising signs of inhibiting growth of human cancer cells without destroying nearby healthy ones. Control Satellite images are used to identify S. molesta in reservoirs in Texas. Biological control The weevil species Cyrtobagous salviniae, found in the native distribution of S. molesta, is being studied as a biocontrol. C. salvinae was first used as a biological control in Australia at Lake Moondarra, a recreational lake in Mount Isa, Queensland in 1980. By mid-1981, the weevil had reduced the population to a few small patches. It ate the leaves of the weed, but preferred the buds. Its larvae ate the roots, rhizomes, and the buds. As the plant died, it turned brown and sank to the bottom of the waterway and decomposed. This weevil was used with success in other parts of the world (13 tropical countries) such as the Sepik River in Papua, Sri Lanka, Lake Ossa in Cameroon as part of an AMMCO project to restore African manatee; Wappa Dam in Queensland, and lagoons (e.g. Kakadu National Park) in the Northern Territory, Australia. The giant gourami has long been known to prefer S. molesta and feed on it voraciously. It has been successfully used to control S. molesta in reservoirs of Sri Lanka. Mechanical control Plants are removed by machine or harvesting equipment and by hand; the latter is suitable only for small infestations. Harvesting equipment can encounter difficulties as it cannot remove all of the infestation, cannot access shallow areas, and can be inhibited by large masses of the plant. Once removed, the plant must be dried, burnt, or disposed of in a manner that ensures it will not re-enter the waterway. Other methods to control the aquatic weed are dredging and chaining. Chemical control Chemical control on S. molesta is difficult as it does have some resistance to herbicides. The chemical fluridon has been successfully used, but it requires prolonged contact and is not effective if it is suddenly diluted by rainwater or any other influx of water. Other chemicals, such as hexazinone, diquat, and double-chelated copper are used together to kill S. molesta. ==References==