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Alligator
Weed
(Alternanthera philoxeroides)
Alligator Weed is somewhat unique in that it can grow in an aquatic
environment, where it can be free floating or rooted to the substrate
with stems and leaves extending over the water, or as a terrestrial
plant. It is an introduced plant, and is declared as a Category
W1 weed under the Noxious Weeds Act 1993 in most areas, and Category
W2 Noxious plant in Maitland and Newcastle.
Similar
Species
Could
be mistaken for Enydra or Water Primrose.
Propagation
Alligator Weed does not produce viable seed. Propagation is from stem
fragments which, when broken from the parent plant, can grow to form
a new plant.
Distribution
Major infestations occur in Port Stephens and Maitland local government
areas, with minor infestations in Newcastle, Lake Macquarie, Wyong,
and Gosford regions.
Control
Measures
Physical control: As propagation of Alligator Weed is by vegetative
means, mechanical control can be very difficult, and may cause expansion
of the infestation due to the fragmentation of the plant. There is also
the problem of disposal, as Alligator Weed can grow as a terrestrial
plant. Unless spoil containing fragments are buried at least 3 metres
below ground, it will regenerate.
Herbicide control: Control in aquatic situations is restricted
to products based on Glyphosate. Results using these herbicides are
variable, and repeated applications will be required. Terrestrial infestations
can be treated with Glyphosate or Metsulfuron based herbicides. Repeated
treatments will be required.
Biological control: Insects have been released in the region
with one, the Alligator Weed Flea Beetle, being active. Damage to plants
does not occur until mid to late December, when sufficient numbers of
insects develop. The level of control by this method varies, but can
be effective in destroying above water stems and leaves.
Weed
Information Sheet PDF
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Enydra
(Enydra fluitans)
A native aquatic plant Enydra is becoming more widespread and is causing
some minor problems in the Williams River and some minor creeks. It
can form large floating mats of tangled stems that can be carried down
stream during flood events. This tangled mass of stems can pose a problem
for young animals and children.
Similar
species
Could be mistaken for Alligator Weed or Water Primrose.
Distribution
Can be found in the major rivers and creeks in the region.
Control
measures
Physical control: Mechanical removal will reduce mass, regrowth
will occur.
Herbicide control: No herbicides registered for control.
Biological control: No known agents available.
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Parrots
Feather
(Myriophyllum aquaticum)
Parrots feather is an introduced plant that can be found in shallow
water bodies where it forms thick tangled mats. Presently it is not
a declared Noxious weed, but there are concerns that it has the potential
to become more widespread and become a serious problem. Please report
any suspected infestations.
Similar
species
Could be mistaken with Cabomba and Hornwort.
Propagation
Propogation is by vegetative means, as seeds produced are not fertile.
Major cause of spread appears to be in floods or on machinery.
Distribution
Isolated infestations only at this time, with minor infestations in
the Port Stephens, Maitland, Cessnock and Wyong areas.
Control
measures
Physical control: Mechanical control can be effective in removing
the bulk of the plant, however as the plant can grow from fragments
it is unlikely that total control could be achieved using this method.
Herbicide control: Only limited number of herbicides registered
at this time.
Biological control: No agents available at this time.
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Water
Primrose
(Ludwigia peploides ssp montividensis)
Water
Primrose is a native plant that sometimes causes problems in areas where
high nutrient levels occur. Under normal conditions it should not be
a problem, however the floating stems can grow 4 to 5 metres in length
and become a tangled mass that may get drawn into pump inlets. This
mass can also be a hazard for young children.
Similar
species
Could be mistaken for Enydra or Alligator Weed.
Distribution
Widespread throughout the lower Hunter and Central Coast.
Control
Measures
Physical control: Water Primrose will not survive if removed
from the water and placed in a dry area. Tangled mats will be very heavy
and difficult to remove.
Herbicide control: There are registered herbicides available.
Biological control: There are native insects that will attack
Water Primrose. These may not completely kill plants, but will reduce
the overall mass.
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