[a complex consisting of Salvinia auriculata Aubl.
[SAVAU], Salvinia molesta D.S. Mitch. [SAVMO], Salvinia biloba Raddi,
Salvinia herzogii de la Sota][all are CDFA list: C][all are Federal
Noxious Weeds] Photographs Maps
giant salvinia, karibaweed, African
pyle or payal, butterfly fern, eared watermoss, aquarium watermoss,
Salvinia hispida Kunth, Salvinia rotundifolia Willd.,
Salvinia natans auct. non (L.) All.
DESCRIPTION: A complex of closely related perennial floating
aquatic ferns that are difficult to distinguish from one another.
Salvinia is often grown as an aquatic ornamental, but has
escaped cultivation and become noxious in many regions worldwide.
Depending on environmental conditions, plants exhibit a range
of growth forms, from the primary invading form with small flat
leaves to the tertiary or mat form with large, crowded, folded
leaves. Under favorable conditions plants can form dense mats
more than ½ m (2 ft) thick. Mats can limit recreational
activities on lakes and waterways, increase flooding and stagnation,
displace native plants and animals, and decrease water quality.
Where it could be carefully managed, Salvinia has been
used to remove excess nutrients and other pollutants from water.
Dried plants make satisfactory mulch. Introduced from tropical
South America. The salvinia weevil (Cyrtobagus salvinae)
has been successfully used as a biocontrol agent in Africa and
Australia. The weevil has been accidentally introduced into the
Stems horizontal just below water surface, sometimes branched.
Leaves 3-whorled, with 2 floating, 1 submerged. Floating leaf
upper surfaces densely covered with water-resistant egg-beater-shaped
hairs ~ 2-4 mm long that diverge into 4 branches near the top
and fuse together at the tips. Floating leaves of the primary
form are flat, well spaced, +/- oval with slightly lobed bases
to obovate with wedge-shaped bases, ~ 8-15 mm wide. Tips rounded
or acute. Floating leaves of the tertiary form are densely crowded,
tightly folded upwards along the midvein, deeply 2-lobed at the
tip, ~ 25-60 mm wide when unfolded, typically broader than long.
Floating leaves of the secondary form are intermediate to the
primary and tertiary forms. Submerged leaves are root-like, whitish,
finely dissected into several filaments up to 2 cm long with hair-like
projections along the length.
and UNDERGROUND STRUCTURES: True roots lacking.
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STRUCTURES: Variable. Some filaments of submerged leaves may
develop chains or clusters of tiny ovoid spore-bearing structures
(sporocarps) ~ 1-3 mm in diameter.
CHARACTERISTICS: Partial plant death often stimulates dormant buds
HABITAT: Still and
slow-moving waters of lakes, ponds, reservoirs, rivers, marshes,
ditches, rice fields. Grows best in nutrient-rich water in tropical
climates. Tolerates mild temperate conditions, some salinity,
and occasional frost, but not prolonged periods of freezing temperatures.
Dense mats do not develop at temperatures below 10º C (50º
molesta has escaped cultivation and is spreading in the Southern
U.S., particularly Texas, and as far west as the lower Colorado
River in Arizona and California. At publication time, populations
have naturalized in the Colorado River drainage and have invaded
some canals in the Sonoran Desert (Imperial Co.). Salvinia
is sometimes offered for sale as an aquatic ornamental. Introductions
may be expected to persist wherever water hyacinth is established.
vegetatively by stem fragments. Each node has up to 5 dormant
buds. Older stems separate from nodes as more buds develop. Fragments
disperse primarily with wind, water currents, flooding, and human
activities. Some protected dormant buds of mat-form plants can
survive dry conditions for long periods, up to 2 years in one
case. Salvinia molesta and S. herzogii are functionally
sterile hybrids. The other 2 species can develop fertile spores.
Under optimal conditions, plants can double their biomass in as
little as 2-3 days.
FAVORING/DISCOURAGING SURVIVAL: Removing and destroying fragments from boat propellers,
docking lines, fishing gear, and other equipment can help prevent
the spread of salvinia.
Unlike innocuous Salvinia species, potentially noxious salvinia
has egg-beater-shaped hairs ~ 2-4 mm long on the upper surfaces of floating
leaves that are easiest to see on young leaves growing under
sunny conditions. Hairs can become damaged on old leaves or may not develop
on shaded plants.
Prevention: Salvinia species have spread via contaminated
aquatic plant stocks, by water craft transport between bodies of water, by moving
water, and by sale and exchange of Salvinia plant material. The current limited
distribution of Salvinia makes prevention the most feasible strategy for limiting
Mechanical: Complete removal of Salvinia by mechanical
harvest is very difficult and costly on large infestations. Plants may regenerate
from small fragments and rapidly reinfest cleared areas.
Chemical: Some herbicides which have been used to control
giant salvinia include Diquat at 1-2 kg/ha, fluridone at 20 parts per billion,
diquat at 3% plus copper at 5%. All of these herbicides and herbicide combinations
provided good to excellent control in Salvinia. Large scale applications of
herbicides may result in a rapid loss of oxygen from water bodies due to the
exceedingly large amount of dead plant material that sinks to the bottom.
Biological: The weevil Cyrtobagous salviniae has been highly
successful in dramatically reducing Salvinia molesta infestations in several
countries worldwide. However, the weevil has not been successful against S.
auriculata. Additional research is being conducted to better understand the
Cyrtobagous complex in relation to specificity on Salvinia species.
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