The City of Cape Town would like to inform the public that the Pine trees in the Tygerberg Nature Reserve have been infected with pitch canker. The Tygerberg Nature Reserve is one of over 30 nature reserves and natural sites managed by the City.
As a result of the problem, affected trees within the picnic area and Pine Alley will be thinned by 50%, while those that fall outside the high intensity leisure zonation area (see map) will be removed completely.
Pine pitch canker is a virulent and incurable fungal disease of Pine trees caused by the fungus Fusarium circinatum, which is transmitted by the deodar weevil, Pissodes nemorensis. It is reported that this disease has affected Pine trees in America and is now affecting trees all over the Western Cape. Earlier this year the first report of pitch canker on mature Pinus radiata in a Tokai plantation in the Western Cape was published in ‘Australian Plant Pathology.’
Infected trees exhibit numerous symptoms including the appearance of canker (i.e. small areas of dead tissue that grow slowly, often over a period of years), with the exception of old trees that are under stress. This is the case with the trees in the Tygerberg Nature Reserve. As these trees are very old, stress is prevalent and, over the next couple of years, all of the trees will die. Additional symptoms include discoloration on the branches, trunk and exposed roots. The fungus most noticeably infects branches from the tips down, turning needles brown, and creates a flow of amber pitch that runs down the trunk. At this stage it has been reported that the Pine pitch canker cannot be eradicated.
In younger plantations the 50% thinning method is used to alleviate stress caused by competition for water and nutrients. This method will be applied in the picnic area and along Pine Alley as it has proved successful elsewhere. Diseased trees would be the target of the thinning in the picnic area but the aim is to try and get an even spacing, leaving trees for shade for another couple of years. Shade structures will eventually be constructed and indigenous trees planted to replace the felled pines.
All of the trees below the tar road and outside the picnic area (such as those on Meyboom Road in Plattekloof) will be removed as they fall outside the high intensity leisure zonation area, as per the Nature Reserve’s accepted management plan*. This plan defines the high intensity leisure zonation as “high use landscapes that are often largely transformed, which are managed largely to support visitor activities more dependent on facilities, education and administrative functions of reserves. The activities and infrastructure in these areas should be managed to minimise impacts on biodiversity and visitor experiences in other zones”.
Over the next two years, the remaining trees will be assessed on a continual basis. The main danger with trees infected with pitch canker is that if they lose branches and if the whole tree is dead, there is an increased risk of trees falling down. This poses a serious threat to the health and safety of visitors and staff alike.
Members of the public can contact the Tygerberg Nature Reserve for more information on 021 913 5695 or via e-mail to tygerberg.naturereserve@capetown.gov.za.
For more information on the City’s nature reserves, visit www.capetown.gov.za/naturereserves.
