Australia. Shop display in Mackay store raises alarm about aquatic weeds
A ceramic pot display in a Mackay store recently caught the eye of a
land protection officer, not because he liked the display but because
it contained water lettuce and salvinia - Class 2 declared aquatic weeds.

"Corey Bell, who works for Biosecurity Queensland, said the store
proprietor had collected the plants from a nearby pond to enhance the
pot display,'' Minister for Primary Industries and Fisheries and
Member for Mackay Tim Mulherin said. "It is an offence under the Land
Protection (Pest and Stock Route Management) Act 2002 to introduce,
keep, release, take, transport or supply any Class 1 or Class 2 weed
pest without a Declared Pest permit," Mr Mulherin said

"While the store was not actually selling the plants, they had still
broken the law by taking and transporting a declared weed. The major
aquatic weed pests in the Mackay region are water lettuce, salvinia,
water hyacinth and hymenachne, all of which are Class 2. It is the
responsibility of landholders to control such weeds and stop any spread."

Invasive weeds such as parthenium, Giant Rats Tail grass and rubber
vine also fall into this Class 2 category.

"It is illegal to take declared aquatic weeds from local waterways,
transport them, keep them at home, dump them from a pond or fish tank
into any waterway or stormwater drain or supply them to anyone else.
The maximum penalties for the transport through to commercial supply
of declared Class 2 aquatic weed pests range from $15,000 to a fine of
$30,000. Just one small plant fragment can rapidly multiply and
completely choke a waterway,'' Mr Mulherin said.

"In warm, sunny conditions and lots of nutrients a plant such as
salvinia can double in volume every two to three days. The
environmental impacts on our waterways can be devastating with reduced
sunlight penetration leading to native plant decomposition. The flow
on effect is oxygen depletion resulting in fish kills and high plant
transpiration can lead to a four-fold increase in water loss."

In these situations, the resulting thick mat of aquatic weed is a
physical barrier for birds and animals trying to access water and it
is also a health risk to humans and livestock. It can damage pumping
and irrigation equipment and during flood event, the huge volume of
weed can damage infrastructure such as fences and bridges.

Mr Bell said biological control agents were available for the three
aquatic weed species, but their effectiveness varied.

"You can use chemical controls with registered herbicides and
mechanical control such as aquatic weed harvesters but this is
expensive," he said. "The best way to prevent the spread of aquatic
weeds is to stop the indiscriminate introduction of these pests into
our waterways from home aquariums."

For identification of these weeds or advice on control methods,
contact the local authority weeds officer or DPI&F Biosecurity
Queensland or the DPI&F Business Information Centre on 13 25 23.

Image: A daunting infestation of water lettuce on a local lagoon
system which poses a real environmental risk impacting on water
quality, fish and bird life.
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