Economic damage. Mats of S. molesta

Economic damage. Mats of S. molesta (referred to hereafter as salvinia) impede access to and use of waterways for commercial and recreational purposes and degrade waterside aesthetics (Fig. 1). Mats reduce habitats for game birds, limit access to fishing areas, and probably alter fisheries, all with negative economic consequences. Salvinia can clog water intakes and interfere with agricultural irrigation, water supply, and electrical generation. It provides habitats for vectors of human disease with serious socioeconomic impacts.
In developing countries, the impact of salvinia can be devastating because weed mats block the use of
Figure 1. Salvinia molesta D.S. Mitchell
covering a farm pond in Texas restricts
commercial and recreational use and degrades aesthetics. (Photography by T. Center.)
waterways for transportation, cutting off access to important services, farm lands, and hunting grounds. The harm from salvinia mats to fisheries also can be very significant to communities dependent on fish for local consumption (sometimes as the main source of protein) or in areas where fish sales are the main source of cash income (Bennett, 1966; Thomas and Room, 1986). Salvinia also is a weed of paddy rice that reduces production by competing for water, nutrients and space (Anon., 1987).

Ecological damage. The ability to grow very quickly (Cary and Weerts, 1983; Mitchell and Tur, 1975; Mitchell, 1978/9; Room, 1986) and blanket water bodies makes salvinia an aggressive and competitive weed (Fig. 2). Initially, salvinia forms a single layer over water, but with continued growth the mats become multi-layered and can reach up to 1 m in thickness (Thomas and Room, 1986). Thick mats support other colonizing plants, and the high biomass and stability of such mats make them difficult to dislodge and destroy (Storrs and Julien, 1996).
Plants and animals dependent on open water to gain sunlight, oxygen, and space for sustenance and growth, or for landing, fishing, nest building, or mating, are displaced
Figure 2. Salvinia molesta D.S. Mitchell
covering a waterbody and supporting the
growth of other plant species in Kakadu
National Park, Australia. (Photograph by
M. Julien.)
by dense salvinia infestations. Water under mats of salvinia has a lower oxygen concentration (due to reduced surface area of water available for oxygenation, inhibition of photosynthesis by submerged plants, and consumption of dissolved oxygen by decaying salvinia), higher carbon dioxide and hydrogen sulphide concentrations, lower pH, and higher temperatures than nearby open water (Mitchell, 1978; Thomas and Room, 1986).
Through high growth rates and slow decomposition rates, salvinia reduces the concentration of nutrients that would otherwise be available to primary producers and organisms that depend on them (Sharma and Goel, 1986; Storrs and Julien, 1996).
Mats of salvinia provide ideal habitat for Mansonia mosquitoes, a principal vector of rural elephantiasis in Sri Lanka (Pancho and Soerjani, 1978), and for other mosquito species involved in the transmission of encephalitis, dengue fever, and malaria (Creagh, 1991/92). Two species of Mansonia that occur in the United States, Mansonia dyari Belkin and Mansonia titillans (Walker), have been implicated in the transmission of St. Louis encephalitis and Venezuelan equine encephalitis, respectively (Lounibos et al., 1990).
Extent of losses. The most detailed assessment of costs caused by salvinia was conducted in Sri Lanka using 1987 as the base year (Doeleman, 1989). Paddy rice losses, fishing losses, other losses (power generation, transport, washing and bathing, etc.), health costs, abatement costs, and economic benefits were considered. No environmental costs were included, but they were recognized as important. There were no identified benefits from salvinia. Total costs associated with salvinia were estimated to be between 24.7 million and 56.7 million rupees (in Australian dollars, between 0.9 and 2.1 million) for 1987. This information was used to determine the benefits from biological control over the following 25 years. The benefits were 53 rupees or dollars per rupee or dollar invested, or 1,673 man-hours per man-hour invested.
Using this information as a guide, Room and Julien (1995) estimated that the annual benefits gained from successful biological control of salvinia worldwide were approximately $150 million U.S.
Geographical Distribution
The native range of salvinia is an area in southeastern Brazil (Forno and Harley, 1979). Its first recorded exotic establishment was in Sri Lanka in 1939 (Williams, 1956). It has since become established in India (Cook and Gut, 1971), Australia (Room and Julien, 1995), Papua New Guinea (Mitchell, 1979), Cuba, Trinidad, Guyana, Columbia (Holm et al., 1979), South Africa (Cilliers, 1991), Botswana (Edwards and Thomas, 1977), Kenya, Zambia (Mitchell and Tur, 1975), Namibia (Forno and Smith, 1999), Madagascar (Room and Julien, 1995), Ghana and Cote D’Ivoire (M. Julien, pers. obs.), Indonesia (Java, Borneo, Sulawesi), Malaysia (mainland Sabah, Sarawak) (R. Chan, pers. comm.), the Philippines (Pablico et al., 1989), Fiji (Kamath, 1979), and New Zealand (Randall, 1996).
Salvinia was first reported outside of cultivation in the United States in 1995 at a pond in southeastern South Carolina (Johnson, 1995). It was eradicated before spread occurred. It was next found in Houston, Texas, in May 1998, and then at other sites in Texas and in Louisiana during 1998. During 1999 it was found in ponds and rivers in Alabama, Arizona, California, Florida, Georgia, Hawaii, Mississippi, and Oklahoma (Jacono et al., 2000; see also Jacono’s web site). Salvinia is readily available for purchase in the United States, particularly through the Internet.
Background Information on Pest Plant
Taxonomy
The aquatic fern family Salviniaceae is placed within the order Hydropteridales and consists of a single genus, Salvinia. Ten species of Salvinia occur worldwide (Herzog, 1935; de la Sota, 1962, 1963, 1964, 1982; Mitchell, 1972). None are native to the United States (Jacono et al., 2000) although seven species
originate in the Americas (de la Sota, 1976). Salvinia molesta was given recognition as a species in 1972 (Mitchell, 1972) and is grouped within the Salvinia auriculata complex, together with Salvinia auriculata Aublet, Salvinia biloba Raddi, and Salvinia herzogii de la Sota (Mitchell and Thomas, 1972). Species within this complex are characterized by the presence of divided but apically joined "basket" hairs on the abaxial surface, which produce an "egg-beater-like" appearance (Fig. 3a) (de la Sota, 1962; Mitchell and Thomas, 1972; Forno, 1983). Salvinia molesta can be distinguished from species within the S. auriculata complex by the arrangement of sporangia, the shape of sporocarps (Mitchell and Thomas, 1972; Mitchell, 1972), and by the pattern of leaf venation (Forno, 1983).
The accepted common name is salvinia, but it also is called Kariba weed, water fern, or African pyle (in Africa); giant azolla or Australian azolla (in the Philippines); and giant salvinia, water spangles, or floating fern (in the United States).
Salvinia minima Baker, the only other Salvinia species present in the United States also is exotic and can be distinguished by the presence of divided hairs on the abaxial leaf surface that are spreading and free at the tips (Fig. 3b).
Figure 3a. Salvinia species in the
United States can be distinguished by
their leaf hairs. In Salvinia molesta the
hairs form an 'eggbeater' shape at the
tips. (Photographs by M. Julien.)


Figure 3b. In Salvinia minima the hairs
are separated at the tips. (Photographs
by T. Center.)

Biology
Plant form. Salvinia is a free-floating aquatic fern with a horizontal rhizome just beneath the water surface (Bonnet, 1955; Room, 1983). Each plant is a colony of ramets. Each ramet comprises an internode, a node, a pair of floating leaves, the submerged ‘root,’ and associated buds. The "root" is a modified leaf that looks and functions like a root (Croxdale 1978, 1979, 1981).
Salvinia is morphologically variable, primarily in response to the level of crowding and availability of nutrients. These two factors are largely independent of one another. There are three growth forms, with a continuum among them, that are associated with the degree of crowding experienced by the plant (Mitchell and Tur, 1975).
The primary form (Fig. 4a) occurs as isolated plants in the initial ‘invading’ stage of an infestation. This form has small, oval leaves less than 15 mm wide that lie flat on the water surface.
The secondary form (Fig. 4b) occurs when plants have been growing over open water for some time, either freely or on the edge of stable mats. Internodes are longer, with larger, boat-shaped (slightly keeled) leaves that have rounded apices and are variable in size, but are normally between 20 mm and 50 mm wide. The entire lower leaf surface is in contact with the water.
The tertiary form (Fig. 4c) occurs when plants are growing in crowded mat conditions associated with mature infestations. Internodes are short with large heart-shaped, or oblong and deeply keeled leaves up to 60 mm in width when fully opened. The undersides of adjacent leaves are in contact with each other.
Figure 4a. The primary form of Salvinia
molesta D.S. Mitchell. (Photographs by M. Julien.)


Figure 4b. The secondary form of Salvinia molesta D.S. Mitchell. (Photographs by M. Julien.)


Figure 4c. The tertiary form of Salvinia molesta D.S. Mitchell. (Photographs by M. Julien.)
Growth and reproduction. Salvinia is pentaploid, has a chromosome number of 45, and is incapable of sexual reproduction (Loyal and Grewal, 1966). Each node bears a series of up to three axillary buds that develop successively under normal growing conditions (Room, 1988), and up to six in response to damage (Julien and Bourne, 1986). The number of axillary buds that grow, the rat

Results (Indonesian) 1:

Kerusakan ekonomi. Tikar S. molesta (disebut kiambang) menghambat akses ke dan penggunaan saluran air untuk tujuan komersial dan rekreasi dan menurunkan tepi Sungai estetika (Fig. 1). Tikar mengurangi habitat burung permainan, membatasi akses ke daerah Perikanan, dan mungkin mengubah Perikanan, semua dengan konsekuensi ekonomi negatif. Kiambang dapat menyumbat asupan air dan mengganggu Irigasi Pertanian, pasokan air dan listrik generasi. Ini menyediakan habitat vektor penyakit manusia dengan dampak sosial ekonomi yang serius.Di negara berkembang, dampak kiambang dapat menghancurkan karena gulma tikar memblokir penggunaan Gambar 1. Kiambang molesta DS Mitchell meliputi kolam farm di Texas membatasi penggunaan komersial dan rekreasi dan estetika. (Fotografi oleh T. Pusat.)perairan transportasi, memotong akses ke layanan penting, tanah-tanah pertanian dan taman berburu. Kerugian dari tikar kiambang Perikanan juga dapat menjadi sangat penting bagi masyarakat yang bergantung pada ikan untuk konsumsi lokal (kadang-kadang sebagai sumber utama protein) atau di daerah di mana ikan penjualan sumber utama pendapatan tunai (Bennett, 1966; Thomas dan kamar, 1986). Kiambang juga gulma padi yang mengurangi produksi bersaing untuk air, nutrisi dan ruang (Anon., 1987).Ecological damage. The ability to grow very quickly (Cary and Weerts, 1983; Mitchell and Tur, 1975; Mitchell, 1978/9; Room, 1986) and blanket water bodies makes salvinia an aggressive and competitive weed (Fig. 2). Initially, salvinia forms a single layer over water, but with continued growth the mats become multi-layered and can reach up to 1 m in thickness (Thomas and Room, 1986). Thick mats support other colonizing plants, and the high biomass and stability of such mats make them difficult to dislodge and destroy (Storrs and Julien, 1996).Plants and animals dependent on open water to gain sunlight, oxygen, and space for sustenance and growth, or for landing, fishing, nest building, or mating, are displaced Figure 2. Salvinia molesta D.S. Mitchell covering a waterbody and supporting the growth of other plant species in Kakadu National Park, Australia. (Photograph by M. Julien.)by dense salvinia infestations. Water under mats of salvinia has a lower oxygen concentration (due to reduced surface area of water available for oxygenation, inhibition of photosynthesis by submerged plants, and consumption of dissolved oxygen by decaying salvinia), higher carbon dioxide and hydrogen sulphide concentrations, lower pH, and higher temperatures than nearby open water (Mitchell, 1978; Thomas and Room, 1986).Through high growth rates and slow decomposition rates, salvinia reduces the concentration of nutrients that would otherwise be available to primary producers and organisms that depend on them (Sharma and Goel, 1986; Storrs and Julien, 1996). Mats of salvinia provide ideal habitat for Mansonia mosquitoes, a principal vector of rural elephantiasis in Sri Lanka (Pancho and Soerjani, 1978), and for other mosquito species involved in the transmission of encephalitis, dengue fever, and malaria (Creagh, 1991/92). Two species of Mansonia that occur in the United States, Mansonia dyari Belkin and Mansonia titillans (Walker), have been implicated in the transmission of St. Louis encephalitis and Venezuelan equine encephalitis, respectively (Lounibos et al., 1990).Extent of losses. The most detailed assessment of costs caused by salvinia was conducted in Sri Lanka using 1987 as the base year (Doeleman, 1989). Paddy rice losses, fishing losses, other losses (power generation, transport, washing and bathing, etc.), health costs, abatement costs, and economic benefits were considered. No environmental costs were included, but they were recognized as important. There were no identified benefits from salvinia. Total costs associated with salvinia were estimated to be between 24.7 million and 56.7 million rupees (in Australian dollars, between 0.9 and 2.1 million) for 1987. This information was used to determine the benefits from biological control over the following 25 years. The benefits were 53 rupees or dollars per rupee or dollar invested, or 1,673 man-hours per man-hour invested.Using this information as a guide, Room and Julien (1995) estimated that the annual benefits gained from successful biological control of salvinia worldwide were approximately $150 million U.S.Geographical DistributionThe native range of salvinia is an area in southeastern Brazil (Forno and Harley, 1979). Its first recorded exotic establishment was in Sri Lanka in 1939 (Williams, 1956). It has since become established in India (Cook and Gut, 1971), Australia (Room and Julien, 1995), Papua New Guinea (Mitchell, 1979), Cuba, Trinidad, Guyana, Columbia (Holm et al., 1979), South Africa (Cilliers, 1991), Botswana (Edwards and Thomas, 1977), Kenya, Zambia (Mitchell and Tur, 1975), Namibia (Forno and Smith, 1999), Madagascar (Room and Julien, 1995), Ghana and Cote D’Ivoire (M. Julien, pers. obs.), Indonesia (Java, Borneo, Sulawesi), Malaysia (mainland Sabah, Sarawak) (R. Chan, pers. comm.), the Philippines (Pablico et al., 1989), Fiji (Kamath, 1979), and New Zealand (Randall, 1996).Salvinia was first reported outside of cultivation in the United States in 1995 at a pond in southeastern South Carolina (Johnson, 1995). It was eradicated before spread occurred. It was next found in Houston, Texas, in May 1998, and then at other sites in Texas and in Louisiana during 1998. During 1999 it was found in ponds and rivers in Alabama, Arizona, California, Florida, Georgia, Hawaii, Mississippi, and Oklahoma (Jacono et al., 2000; see also Jacono’s web site). Salvinia is readily available for purchase in the United States, particularly through the Internet.Background Information on Pest PlantTaxonomyThe aquatic fern family Salviniaceae is placed within the order Hydropteridales and consists of a single genus, Salvinia. Ten species of Salvinia occur worldwide (Herzog, 1935; de la Sota, 1962, 1963, 1964, 1982; Mitchell, 1972). None are native to the United States (Jacono et al., 2000) although seven species originate in the Americas (de la Sota, 1976). Salvinia molesta was given recognition as a species in 1972 (Mitchell, 1972) and is grouped within the Salvinia auriculata complex, together with Salvinia auriculata Aublet, Salvinia biloba Raddi, and Salvinia herzogii de la Sota (Mitchell and Thomas, 1972). Species within this complex are characterized by the presence of divided but apically joined "basket" hairs on the abaxial surface, which produce an "egg-beater-like" appearance (Fig. 3a) (de la Sota, 1962; Mitchell and Thomas, 1972; Forno, 1983). Salvinia molesta can be distinguished from species within the S. auriculata complex by the arrangement of sporangia, the shape of sporocarps (Mitchell and Thomas, 1972; Mitchell, 1972), and by the pattern of leaf venation (Forno, 1983).The accepted common name is salvinia, but it also is called Kariba weed, water fern, or African pyle (in Africa); giant azolla or Australian azolla (in the Philippines); and giant salvinia, water spangles, or floating fern (in the United States).Salvinia minima Baker, the only other Salvinia species present in the United States also is exotic and can be distinguished by the presence of divided hairs on the abaxial leaf surface that are spreading and free at the tips (Fig. 3b). Figure 3a. Salvinia species in the United States can be distinguished by their leaf hairs. In Salvinia molesta the hairs form an 'eggbeater' shape at the tips. (Photographs by M. Julien.) Figure 3b. In Salvinia minima the hairs are separated at the tips. (Photographs by T. Center.)BiologyPlant form. Salvinia is a free-floating aquatic fern with a horizontal rhizome just beneath the water surface (Bonnet, 1955; Room, 1983). Each plant is a colony of ramets. Each ramet comprises an internode, a node, a pair of floating leaves, the submerged ‘root,’ and associated buds. The "root" is a modified leaf that looks and functions like a root (Croxdale 1978, 1979, 1981).Salvinia is morphologically variable, primarily in response to the level of crowding and availability of nutrients. These two factors are largely independent of one another. There are three growth forms, with a continuum among them, that are associated with the degree of crowding experienced by the plant (Mitchell and Tur, 1975).The primary form (Fig. 4a) occurs as isolated plants in the initial ‘invading’ stage of an infestation. This form has small, oval leaves less than 15 mm wide that lie flat on the water surface.The secondary form (Fig. 4b) occurs when plants have been growing over open water for some time, either freely or on the edge of stable mats. Internodes are longer, with larger, boat-shaped (slightly keeled) leaves that have rounded apices and are variable in size, but are normally between 20 mm and 50 mm wide. The entire lower leaf surface is in contact with the water.The tertiary form (Fig. 4c) occurs when plants are growing in crowded mat conditions associated with mature infestations. Internodes are short with large heart-shaped, or oblong and deeply keeled leaves up to 60 mm in width when fully opened. The undersides of adjacent leaves are in contact with each other. Figure 4a. The primary form of Salvinia molesta D.S. Mitchell. (Photographs by M. Julien.) Figure 4b. The secondary form of Salvinia molesta D.S. Mitchell. (Photographs by M. Julien.) Figure 4c. The tertiary form of Salvinia molesta D.S. Mitchell. (Photographs by M. Julien.)Growth and reproduction. Salvinia is pentaploid, has a chromosome number of 45, and is incapable of sexual reproduction (Loyal and Grewal, 1966). Each node bears a series of up to three axillary buds that develop successively under normal growing conditions (Room, 1988), and up to six in response to damage (Julien and Bourne, 1986). The number of axillary buds that grow, the rat