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World's worst weeds waiting to invade
9 October 2000
Weedbuster Week 8 - 15 October
In August this year the exotic weed fringed spider flower was found growing on Darwin's Fort Hill Wharf. In fewer than two months, further infestations have been found at Moil, Bees Creek and Parap.
How the seeds entered Australia is not certain but what is certain is that this plant is one of the world's worst weeds. It invades with stealth and spreads quickly to compete with annual crops such as peanuts, vegetables and melons. Unchecked, it could cause millions of dollars of damage to Australian primary industry and cost further millions in long-term control measures.
A timely warning comes in this, National Weedbuster Week, from Northern Australia Quarantine Strategy's (NAQS) Darwin-based botanist, Andrew Mitchell, who said today that fringed spider flower was one of only four exotic weeds ranked in the highest 'very serious threat' category on the NAQS target list of 41 weeds.
Siam weed is the most destructive and the biggest threat.
"Siam weed is commonly known as 'the world's worst weed'. It is the biggest threat as far as the Northern Territory is concerned because it grows in such abundance in East Timor," Mr Mitchell said.
"Military traffic, United Nations and other aid workers regularly move between Dili and Darwin and each movement of people or equipment increases the risk that Siam weed seeds will move into Darwin."
AQIS carries out strict inspection procedures both pre-departure in Dili and on arrival in Darwin for flights and boats from East Timor
"These tiny parachute seeds get caught in everything from socks to armoured personnel carriers," Mr Mitchell said.
Siam weed grows in dense bushes 2 to 3 metres tall but will scramble over other vegetation and trees forming impenetrable barriers up to 7 metres tall. Growth rates of 20 millimetres a day have been recorded. It produces large quantities of seed with a parachute of white hairs that helps it spread by wind. The seeds have tiny barbs that attach to clothing, footwear, animals, machinery and even spiders' webs. It can re-grow from stem and root fragments. Tall woody stems are a fire hazard in the dry season. Plants survive fire and drought.
Siam weed can be easily identified as it produces masses of small white or pale lilac flowers, always in May to June. NAQS asks residents to be on the lookout for strange weeds in their area: contact Andrew Mitchell on (08) 8999 2104.
For more details
Contact: Kay Carvan, Public Awareness Officer, NAQS
Phone: (08) 8999 2046
or
Contact: Andrew Mitchell
Phone: (08) 8999 2104