Table 4.1
Alien aquatic plant species that are present in South Africa, or that pose significant risks should they be introduced, with basic information on their status,
distribution and control options
Species and common name
Growth form Status and distribution
Impact
Control options
Key references
The
‘Big Bad Five’—species targeted for biological control prior to 2000
Eichhornia crassipes
(Mart.)
Solms. (Pontederiaceae);
Water Hyacinth
Free-floating
Invasive
Widespread in South Africa
Long established
Major impacts
on aquatic
ecosystems
Under substantial biological
control, but needs to be
integrated with chemical
control to be effective
Coetzee et al.
(2011a), Hill and
Coetzee (2017)
Pistia stratiotes
L. (Araceae);
Water Lettuce
Free-floating
Invasive
Widespread in South Africa
Long established
Major impacts
on aquatic
ecosystems
Under complete biological
control
Coetzee et al.
(2011a), Hill and
Coetzee (2017)
Salvinia molesta
D.Mitch.
(Salviniaceae); giant
salvinia/Kariba Weed
Free-floating
Invasive
Widespread in South Africa
Long established
Major impacts
on aquatic
ecosystems
Under complete biological
control
Coetzee et al.
(2011a), Hill and
Coetzee (2017)
Myriophyllum aquaticum
(Vell.) Verdc.
(Haloragaceae); Parrot’s
Feather
Rooted
emergent
Invasive
Widespread in South Africa
Long established
Major impacts
on aquatic
ecosystems
Under complete biological
control
Coetzee et al.
(2011a), Hill and
Coetzee (2017)
Azolla
filiculoides Lam.
(Azollaceae); Red Water
Fern
Free-floating
Invasive
Once widespread in South Africa,
but has been extirpated through
biological control from most
sites
Long established
Major impacts
on aquatic
ecosystems
Under complete biological
control
Coetzee et al.
(2011a), Hill and
Coetzee (2017)
New targets for biological control—2006 to present
Egeria densa
Planch.
(Hydrocharitaceae); Brazilian Waterweed
Submerged
Invasive
Distribution increasing in
South Africa
Long established
Major impacts
on aquatic
ecosystems
Mechanical and chemical control
not effective. Biological control agent released in 2018
Coetzee et al.
(2011b), Hill and
Coetzee (2017),
Smith et al.
(2019)
Hydrilla verticillata
(L.f.)
Royle (Hydrocharitaceae);
Hydrilla
Submerged
Invasive
Restricted to Jozini Dam and downstream into the Pongola River
Long established
Major impacts
on aquatic
ecosystems
Mechanical and chemical control
not effective. Biological control agents available, but not
yet released
Bownes (2010),
Coetzee et al.
(2011b), Hill and
Coetzee (2017)
(continued)
4 Invasive Alien Aquatic Plants in South African Freshwater Ecosystems
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