Five years ago, workers in the Longyandong farm in a suburb of Guangzhou, capital of south China's Guangdong Province, found that trees there were being threatened by an alien vine-like plant.

The plant, with bell-like yellow flowers, was climbing up big trees and rapidly spreading over the hills.

Its fast growth gives rise to a green and dense canopy which blankets native shrubs, even 10-metre-tall trees, until the latter are suffocated.

Over the past five years, the workers have tried all imaginable means to kill the deadly plant, but this has been in vain.

The hills were soon covered. So far, up to 20 hectares of forest have fallen victim to it, according to local people.

It was only a few weeks ago that scientists from Guangzhou managed to identify this deadly species.

Scientists from the South China Botanical Garden, a plant research institute affiliated to the Chinese Academy of Sciences (CAS), found this invasive plant species is native to the tropical regions of Hainan Province and Guangxi Zhuang Autonomous Region, both neighboring Guangdong in southern China.

But it had not reared its ugly head in Guangdong.

Called Jinzhongteng (Merremia boisiana), this plant species belongs to the family of Convolvulaceae or morning-glory, according to Ye Wanhui, a researcher from the botanical garden.

In its original habitats, Ye said, the vine's growth is suppressed by its natural enemies. However, the researchers have yet to find them.

But it encounters no such obstacles in the subtropical region of Guangdong, where the alien species can multiply quickly.

The damage caused by the "pretty tree killer," as it is nicknamed, is greater than the South American Climber (Mikania micrantha), another invasive species notorious for its destruction, according to Ye, who has been involved in the investigation into Jinzhongteng.

"It's one of the most aggressive plant species that has invaded Guangdong," Ye said.

The vine does the greatest amount of damage to young saplings.

In the tree farm where the murderous vine was first discovered, workers use herbicide to get rid of it, but in vain.

Also, manual felling cannot work as the vine cannot be thoroughly uprooted.

"The workers have even tried to get rid of it with fire, but it usually comes back the next year," Ye said.

Three months have passed since new drugs were introduced to suppress of the vine, but no notable progress has been made, according to a report issued by the CAS information office.

Chen Binhui, another researcher from the botanical garden, warns the forest administration should be prepared for the vine to do more damage elsewhere.

Ye and Chen agreed that global warming, which has been evident in China over the past decade, might have contributed to the spread of the vine.

With the weather getting warmer, the vine moves north and takes root in places where it was once unable to survive.

"Even today we still do not know how this species has migrated from Hainan to Guangdong," Ye said, "but one thing is sure, the warm weather has helped."

Chen was quoted by the CAS report as offering some measures to counter this destructive species.

He noted the urgent need to conduct a comprehensive investigation across all of Guangdong Province to make clear the real situation of the vine's distribution for the authorities to launch a timely campaign to wipe it out.

Before any more effective methods are available, one way to exterminate the vine is to cut off its stems and dig up its roots, he added.

But this requires a massive amount of manpower, and the overall effect of this remains unclear, Ye added.

Chen also recommended the introduction of the vine's natural enemies to prevent it from spreading.

But Ye argued that, although this measure sounds reasonable, it could backfire.

He said while the natural enemies, once introduced, may stem the spread of the vine, they may also sabotage the local ecology.

"The natural enemy may become another source of biological invasion and get out of control, as it is also alien to the local environment," Ye said.

The latest statistics from the Ministry of Agriculture show that China has come under attack from more than 400 alien organisms so far and some 20 major biological invasions have occurred throughout the country over the past decade.

The central government sets up a special office this year to tackle this increasingly serious problem and the Ministry of Agriculture has drawn up a plan to cope with biological invasions immediately after they occur.

Hopefully, the plan will be carried out nationwide from next year, according to the ministry.  

(China Daily December 23, 2004)