SUNGAI PETANI: It has been dubbed the “worst weed of the century”, destroying native flora and crops, causing rashes that can leave humans permanently scarred and damaging the intestines of animals that eat it.
Called Parthenium hysterophorus, it was first detected here in September last year in Ulu Yam, Selangor.
But the highly-allergenic plant has since been spotted in Perak, Kedah and Negri Sembilan, raising fears that it has spread throughout the country.
Initial accounts show that the plant has even resisted attempts to control it through weedkillers.
A species of flowering plant native to Mexico, it can cause severe skin disease and hayfever in humans.
It is also toxic to livestock such as goats and cows, causing fevers, ulcers, anorexia and intestinal damage, and can quickly replace native flora by releasing toxic substances, causing massive crop loss.
Similar in appearance to ulam raja, P. hysterophorus is classified as a dangerous pest under the Plant Quarantine Regulations 1981 and can quickly propagate.
According to Professor Dr S. M. Rezaul Karim of Universiti Malaysia Kelantan, this is because one plant, which can reach several feet in height, can produce hundreds of thousands of seeds during its four-week life cycle.
“The seeds can be dormant in the ground for up to 10 years, making it impossible to get rid of.”
In Sg Petani, some areas had been sprayed with herbicide, only to see fresh plants springing anew just days later.
“The weed spreads like wildfire. You can look at examples in other countries, such as Australia which spends millions of dollars yearly trying to control it,” said Dr Karim, who heads the university’s parthenium weed research group.
According to Dr Karim, P. hysterophorus not only competes with other plants for nutrients – it also releases chemicals which damage other plants.
Its effect on people, he said, was particularly worrying as it often grows by the roadside where the public can easily come into contact with it.
“We need to find out how many communities in Malaysia have been affected,” he said.
“In some nations, the rash can become so bad it leaves people permanently scarred. It can take three months for the symptoms to subside,” he said.
Checks by The Star during a recent field trip to Sungai Petani saw the weed growing as high as 1.2m (4 ft) in close proximity to restaurants, paddy fields, businesses and irrigation drains that allow the seeds to hitch a ride to other areas, thus propagating its spread.
According to DOA representatives, the area had been sprayed several times with weedkiller to no avail.
In a media release, the DOA listed several methods of controlling the weed, including destroying the weed in its early stages before it flowers and produces seeds, and curbing it in residential areas using salt water in a 1:4 ratio of salt to water.
The department believes that the weed arrived in Malaysia by way of seeds being carried through imported machinery or in fertiliser.
Among the known affected areas are Kinta, Hulu Perak, Selama, Perak Tengah, Manjung, Kuala Kangsar, Pokok Sena, Hulu Selangor, Kuala Muda, Kota Setar, Seremban and Kuala Pilah.
The DOA’s Plant Biosecurity Division has formed a technical committee on the control, containment and removal of P. hysterophorus that will come up with a standard containment operating procedure and work with state governments to identify and monitor problem areas as well as destroying existing weeds.
State agricultural officers have been briefed on how to deal with the problem while an exercise to identify places where the weed grows is already underway.