New officer, old weed problem

The water hyacinth problem shouldn’t be as bad as it has been in previous flood years.
The water hyacinth problem shouldn’t be as bad as it has been in previous flood years.

WELCOME to our new year edition of Weed of the Month. Clarence Valley Council continues to provide a monthly update on new and existing weeds impacting on our productive and protected environments.

This month council introduces our newest member of the team in the fight against invasive plants in the Clarence Valley.

Shane Landrigan has just started with council this week as a weeds officer. Shane is originally from the Clarence but has been working in the south-east Queensland area on weed programs for a number of years and brings a wealth of knowledge with him.

Shane's role will be to inspect properties for new weed incursions, and encourage and educate landholders to proactively manage weeds.

He will be shown the ropes by Bill Jordan who held the position prior to Shane's appointment. We wish Bill all the best in his retirement.

Water hyacinth eichhornia crassipes

It is worth noting the impact of the aquatic weed water hyacinth after last week's floods. It is recognised as a major aquatic weed and was recently proclaimed as a Weed of National Significance (WONS). It has shown its impact by damaging assets such as fences and watering points, reducing access over properties and roads and loss of feed on paddocks for stock.

The cost is directly felt by landholders as well as council's infrastructure on the floodplain, but it is expected not to be as bad as previous years due to the dry conditions and control work under- taken in the past 18 months.

It is declared as a Class 4 noxious weed which requires "the growth of the plant must be managed in a manner that reduces its numbers, spread and incidence and continuously inhibits its reproduction".

It is difficult to enforce control as many infestations are widely spread across the floodplain in drains and water bodies.

Water hyacinth has a long history of establishment in the valley, noted in a Sydney Morning Herald article dated from 1899.

Hence the high probability to re-infest with seeds that can lay dormant for up to 30 years, making it near impossible to eliminate from our watercourses.

However the flood does present an opportunity to treat remaining plants in watercourses on the floodplain and council will continue to work with affected landholders to come up with viable solutions for its long-term control.

This is evident on Alumy Creek where council is implementing a range of options in consultation with an advisory committee.

These include herbicide control programs and the release of salt water to reduce the impact and distribution of water hyacinth.

The efforts to date have resulted in a reduction of 80% of the infestation from the creek.

An ongoing effort is required from everybody to keep this noxious weed under control.

Weed of the month

Information on water hyacinth

  •  Free-floating perennial that forms large dense mats on water surface
  •  Plant consists of broad leathery leaves, generally bright green in colour; spongy leaf stalks: and a mass of fine, hairy roots
  •  Stems can be erect up to 600mm long; or horizontal vegetative stems (stolons) which produce daughter plants
  •  Flowers are bluish-purple with yellow centre 40 to 70mm across, funnel-shaped
  •  Seeds are 1 to 1.5mm long and roughly egg-shaped - long-lived up to 30 years

Control methods

  •  Early detection and rapid response offer the greatest likelihood of successful control. In large established infestations the aim should be to carry out annual control treatments to reduce the quantity of reproducing plants and restrict seed-bank build-up over long term.
  •  Physical removal - early control efforts can be achieved with pitchforks and dumping accumulated mass on land to die.
  •  Mechanical removal - effective although costly - it can take between 600 to 900 hours to harvest one hectare of dense water hyacinth.
  •  Herbicide controls - a number of herbicides are registered for control - see for more information
  •  Biological control - four insects (two weevils, two moths) from South America have been released by the CSIRO since 1975. All are well established and can be damaging by providing some reduction in flowering and growth rates of the plant.
  •  Cultural control - as part of a control program - nutrient runoff into infested waterways should be minimised. In some situation salty water is able to be naturally introduced into infested waterways.

Information courtesy of NSW DPI -

Topics:  biosecurity water hyacinth weed of the month weeds

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