Following is a question by the Hon.Choy So-yuk and a reply by the Secretary for the Environment and Food, Mrs Lily Yam, in the Legislative Council meeting on July 11th 2001.

Question: It is learned that a large number of trees in Hong Kong are overgrown with Mikania micrantha, a fast growing climbing plant which withers some of them by blocking the sunshine. In this connection, will the Government inform this Council whether it has:

• (a) assessed the damage caused to trees by Mikania micrantha; and
• (b) explored more effective alternatives to manual removal of Mikania micrantha; and
• (c) any measures to curb the proliferation of Mikania micrantha?

Answer: (a) Mikania micrantha is a fast-growing plant capable of climbing over other plants to gain more sunshine. The growth of plants covered by Mikania micrantha over a prolonged period may be impaired as these plants cannot receive enough sunshine.

The Agriculture, Fisheries and Conservation Department (AFCD) and the Leisure and Cultural Services Department (LCSD) have assessed the damage caused to plants by Mikania micrantha. Results have shown that Mikania micrantha has not caused any damage to urban vegetation. LCSD regularly inspects trees and plants within its jurisdiction and undertakes vegetation maintenance work. Whenever Mikania micrantha is found, it will be immediately removed. Other works departments also committheir contractors to carry out regular weeding and removal of climbing plants for the landscaped areas within their jurisdiction.

As regards country parks, Mikania micrantha is found growing in only a few areas, estimated to cover a total area of about 10 hectares, which equals to about 0.025 per cent of the total country park area. AFCD makes regular arrangements for manual removal of Mikania micrantha at the affected areas and the growth of the plant in country parks is under control. As trees grow in country parks are taller and bigger, there is usually not enough sunlight for Mikania micrantha. This environment is not conducive to the growth of Mikania micrantha and the plant has not caused serious harm to the forest.

(b) According to the expert opinion of AFCD, removing Mikania micrantha manually is the most feasible measure for the time being. Other methods, such as using herbicide, may have undesirable impact on the environment. Burning is also not viable as Mikania micrantha is very deep-rooted and is almost impossible to burn out the roots to exterminate the plant and prevent it from regenerating. The use of mechanical means to clear Mikania micrantha is also not recommended as it may cause damage to other plants nearby.

The Afforestation Bureau of Guangdong Province is conducting a "Comprehensive Study on the Preventive and Control Technologies regarding Mikania micrantha" which will last for two years. The objective of the study is to explore more effective preventive and control measures regarding Mikania micrantha. The study should be completed by the end of next year. AFCD is discussing with the Guangdong authorities the feasibility of extending the plan to Hong Kong.

(c) At present, the best way to curb the proliferatioof Mikania micrantha is to take preventive measures at an early stage to check its growth. In this connection, relevant departments will step up their inspection works. If Mikania micrantha is found, eradication work will be conducted as soon as practicable.