If not stopped, a tiny parasite that is killing tens of thousands of pine trees in Guangdong may cause even bigger environmental problems.

Lumberjacks in the province are cutting down trees to stay ahead of nematodiasis, dubbed "forest cancer" by some, a disease that has killed more than 10,000 pine trees in the South China Botanical Garden.

According to a provincial forestry official Wednesday, the disease, usually found in northern parts of the country or abroad, poses a severe threat.

"Nematodiasis has been found in many cities in the province," said Lin Duping, director of the Tree Disease Prevention and Control Department under the Guangdong Provincial Forestry Bureau.

"And we actually face many difficulties in eradicating the disease, one of the three major forest diseases in the world," Lin said.

Caused by a contagious parasite carried by beetles common in forest areas, there is no quick and easy cure for the disease.

In addition to widespread disinfections and cutting down dead trees, Lin said his bureau is also planning to ask forestry departments to raise a species of bee that can kill the beetles that host the tiny parasite and curb the spread of the disease.

Lin also called for tighter controls on imported lumber to prevent nematodiasis from further entering the country.

Wang Weiwen, an official from the Guangzhou Municipal Bureau of Forestry Industry, said many pine trees affected by the scourge in the city have withered. It may have affected more than 86,666 hectares of pine trees or one-third of Guangzhou's total forest area.

A pine tree can die about 40 days after it contracts the disease. According to Wang, all Guangzhou's pine trees will die unless effective measures are taken quickly.

The death of pine trees on this scale could result in serious soil erosion and pollute the upper reaches of the Liuxi River, which winds through one of the major pine forests in Guangzhou and provides drinking water for more than 10 million residents, said Lin Duping.

With a 50 million yuan (US$6 million) of annual economic losses caused by nematodiasis, Guangzhou municipal government has invested more than 10 million yuan (US$1.2 million) to fight the disease over the past three years.

Nematodiasis was first found in Guangzhou four years ago. And the disease has spread to cover more than 963 hectares of the city, including Huadu and Panyu districts and the suburb of Conghua, Wang said.

Lin Duping said Guangdong's nematodiasis was first found in the Shenzhen Special Economic Zone in 1988 and is believed to have come from overseas.

In 1995, nematodiasis spread to the neighboring cities of Huizhou and Dongguan in the eastern part of the prosperous Pearl River Delta region.

By the end of last month, the disease was detected in more than 21,466 hectares of pine forests in the entire province's more than 4.13 million hectares of pine forests.

The province is estimated to be losing between 5 billion yuan (US$600 million) and 10 billion yuan (US$1.2 billion) from nematodiasis.

(China Daily November 18, 2004)