SUNGAI PETANI, MALAYSIA- 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.