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LCQ1: Infection of pine trees

    Following is a question by the Hon Albert Chan and an oral reply by the Secretary for the Environment, Mr Edward Yau, in the Legislative Council today (June 4):


    I have learnt that in recent years, quite a number of pine trees in various parts of Hong Kong, especially Chinese red pines, have been infected, and some of them even died as a result. In this connection, will the Government inform this Council:

(a)  of the respective numbers of pine trees of various species which had been infected and died from infection in each of the past five years; and

(b)  whether the authorities know the causes of infection for the above pine trees, and whether currently there are measures and new methods to prevent pine trees from being infected and dying as a result, so as to reduce the death of pine trees; if there are such measures and methods, of the details; if not, the reasons for that?


Madam President,

(a) In early 1980's, there was mass mortality of the local Chinese Red Pines due to infection by the pine wilt nematode. To control spread of the disease, infected trees were cut down and burnt. Furthermore, planting of the vulnerable Chinese Red Pine was discontinued.  After implementation of these measures, serious outbreaks of the pine wilt disease were no longer found.

    Besides the infection of Chinese Red Pine by pine wilt disease in early 1980s, there were no other record of serious outbreaks of pine trees by disease.

    There has not been any territory wide survey on pine tree in Hong Kong. Therefore, we do not have the annual data on the numbers of pine trees of various species which had been infected and died from infection. However, based on field observations, there were only sporadic deaths of pine trees in recent years. There were no incidents similar to the unusual mortality of pine trees caused by infection in the 1980's.

(b)  Pine wilt nematode is the causal agent of pine wilt disease that could lead to serious losses of trees and woodlands. In this regard, the Agriculture, Fisheries and Conservation Department (AFCD) conducted a survey in 1999 to investigate the pest status of the pine wilt nematode in Hong Kong. Out of the some 1,300 pine tree samples collected, only one sample was found to be infested with the pine wilt nematode. The study concluded that the pest is no longer a threat to the pine tree population in Hong Kong and large scale control programme on this pest is not considered necessary.

    In addition, the AFCD commissioned the Guangdong Forestry Bureau to conduct the study "Survey of forest pests and diseases in Hong Kong" from 2005 to 2007. The findings of the study indicated that the woodland ecosystems in country parks have good natural ability to control pests and disease. The woodlands of country parks are not affected by serious pests or diseases as a whole.

    Healthy trees are resistant to pests and diseases. Spreading of pests and diseases is much more difficult in diverse woodlands.  Hence, maintaining healthy and diverse woodlands is the most effective measure to prevent outbreak of pests and diseases. In this regard, the AFCD has practised mixed planting in establishing new woodlands. Mixtures of seedlings of different tree species have been planted together to allow development of diverse woodlands in future. For existing plantations, particularly those comprising mainly pine trees, the AFCD has planted seedlings of different tree species, so as to enrich species composition and enhance biodiversity.

Ends/Wednesday, June 4, 2008
Issued at HKT 12:16


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