Gist of the Sixth Meeting held on 19 September 2012

1. Progress of Tree Risk Assessment and Management (TRAM)
   • Members were informed of the progress on implementation of the 2012 tree risk management and assessment arrangement by the tree management departments in preparation for the run-up to the rainy season. All departments involved basically completed all the Form 1 and Form 2 assessment for the trees in Category I zone by 31 July 2012. Most of the mitigation works had been completed as well. The exercise was completed within schedule.
   • As regards the review on the methodology of TRAM, the current methodology and scheme adopted by the TMO was in line with international practice. Compared with the overseas practice, the requirements in Hong Kong were in fact already more stringent than those promulgated by the United States Department of Agriculture (USDA).
   • On the related training on tree risk assessment organised by the TMO to equip government and consultants/contractor staff in tree management departments with knowledge of the promulgated tree risk assessment arrangement, the TMO had organised a number of training courses, seminars and workshops from January 2012 to August 2012. Apart from basic training, the TMO had also subscribed to advanced training programmes in tree risk assessment including the Tree Risk Assessment Course & Examination (TRACE), the Tree Hazard Assessment Course with Integrated assessment (British Accredited LANTRA Professional Tree Inspection Qualification) and the Professional Diploma Programme in Arboriculture offered by the School of the Continuing and Professional Studies of the Chinese University of Hong Kong for officers nominated by departments so as to raise the professional competence of departments.
   • To ensure that TRAM work had been professionally carried out, the TMO requested tree management departments to establish an internal audit checking mechanism according to the guidelines on the auditing procedures for TRA issued by the TMO. In addition, the TMO also carried out desktop and field audit checks to ascertain if the promulgated tree risk assessment requirements and methodology were complied with and the required quality of tree risk assessment achieved.
   • A lot of progress had been made to improve the examination system of the TRA internal training and the upkeep of auditing work since TMO with reference to the comments made by the Expert Panel at its 3rd meeting. The TMO were now exploring with local education institutes more training opportunities for tree management personnel at various levels.
   • Members provided views and suggestions to further enhance the TRAM arrangement.
2. Brown Root Rot Disease - Surveillance Programme and Management Strategy
   • Members were briefed on the purpose of the above paper, which was to provide a review on studies on Brown Root Rot (BRR) Disease with emphasis on its diagnosis and management strategy.
   • The BRR disease was prevalent in tropical and subtropical regions for decades. It had come to the attention of the TMO after the outbreak of a few cases locally in recent years. A guideline/ information note on the introduction of BRR disease was promulgated by the TMO to facilitate departments to manage BRR in 2011. In view that the TMO had gathered more first hand information about BRR through direct handling of a number of BRR infected cases and also with reference to relevant literatures, a revised guideline had been prepared by the TMO.
   • The following management measures were proposed :
     1. To minimize the inoculums size by removal of infected trees and dumping the infected parts with proper packing to landfill area.
     2. To disinfect the soil medium by three key methods, namely flooding the field, use of ammonia (urea)-based chemical and soil fumigant for killing BRR on infected wood pieces in the soil medium.
   • As for the treatment of BRR infected trees, there was no effective chemical treatment. Some overseas practices included the use of surgical processes to remove diseased part of the infected tree followed by the application of fungicide, replacement of soil and provision of support for structural stability of the tree might have its merits but it differed from some principles of modern arboriculture in terms of tree defensive against decay through compartmentalization of decay in tree (CODIT). The high cost through such treatment was also not feasible for the number of trees infected with BRR. The TMO would propose a pilot experiment to look into the effectiveness of using biological control agent Trichoderma species to control BRR at the initial stage of infection in Hong Kong.
   • Members discussed the proposed management strategy on BRR and generally supported it and provided views on the proposed revised guidelines on BRR.
3. Proposal of Planter Extension at Park Lane
   • Members were briefed on the proposal of planter extension at Park Lane to improve the growing environment for the OVTs thereat. LCSD proposed to expand the planters horizontally for 2m and longitudinally at strategic locations to improve the growing environment for the OVTs so as to allow tree roots to creep onto and aerial roots down to the new planters.
   • A trial scheme to expand the planter for OVT YTM/6 and YTM/9 horizontally; and YTM/29 longitudinally was proposed to be implemented due to relatively less site constraints thereat. The option and scale of the second phase of the project would be determined by the result of the trial.
   • Members generally supported the proposal and provided views to improve the proposal.
4. Report on Trees Requiring Close Monitoring
   • Members were briefed on the updated situation of LCSD OVT S/9. The LCSD had consulted the Lands Department (LandsD) and Highways Department (HyD) on their proposed extension of planting area of S/9 to improve the growing environment. There was no adverse comment except the one of the proposed extensions might encroach onto a private nursery which was on private land. The TMO and LCSD would further explore with the relevant departments and the private nursery the possibility of extending the planting area and replace the concrete paving of the nursery with porous material.
   • Members supported the improvement proposal and provide views.
   • Members were briefed on the condition of LCSD OVT E/35. In view of current condition of the tree (i.e. dead/dying) and its location adjacent to the walkway inside the Victoria Park which poses risk to the public, it was recommended to remove this tree very soon to eliminate the risk of tree failure. It was also recommended to collect soil and debris samples for laboratory identification of any possible pathogenic fungal disease which might affect the vegetation in the vicinity.
   • Members generally agreed to the recommendations.
5. Site Visit to OVT LCSD CW/73 at Garden Road, CW/5 at Smithfield Junction
   • A site inspection of CW/73 was conducted. Members were briefed on the overall conditions and the assessment of CW/73.
   • Members generally expressed grave concern on the structural integrity of the subject tree and provided the following views :
     1. The overall structural condition of the subject tree was very poor;
     2. The decayed parts on both the main trunk and the scaffold branch were serious and not recoverable as the rate of decay was faster than regrowth. This had compromised the structural stability of the subject tree;
     3. The existing cabling system might not be effective to mitigate the risk of failure of the subject tree;
     4. The subject tree leaned towards the Garden Road which was of high traffic flow;
     5. The subject tree should either be felled or to retain the main trunk only in view of the public safety.
   • Members agreed to remove it to eliminate the risk to the targets on the Garden Road.
   • A site inspection of CW/5 was conducted. Members were briefed on the overall conditions and the analysis of CW/5.
   • Members generally opined that the overall structural condition of the subject tree was poor and provided the following views :
     1. There were cracks and decay at the union of the codominant trunks which might have compromised their stability;
     2. The aesthetic value of the subject tree was poor as it was not the original tree (trunk) but the regrowth of the aerial roots;
     3. The resprouts resulted from the previous heavy crown reduction would require a lot of maintenance works i.e. frequent pruning, which might not be worthwhile to spend the public money;
     4. There was no imminent danger of failure and it might be feasible to help the subject tree to recover such as training of the aerial roots, structural pruning and installation of a permanent prop, however, spending too much public money on the subject tree was not recommendable;
     5. The local community and all stakeholders should be consulted on the compensatory planting scheme if the subject tree was proposed to be felled.
   • Members agreed that LCSD would report the updated conditions as well as the pros and cons of various options to the Central and Western District Council for consultation before deciding on the way forward.