Melbourne’s remembrance monument lone pine is located at the Shrine Reserve. We are saddened to say that the outcome was not as we hoped and the tree was removed in late August 2012.
Symptoms evident on the tree back in May led to the intitial diagnosis of the disease Diplodia Blight (Diplodia pinea syn. Sphaeropsis sapinea). As evidenced by the foliage that was present when we assessed it again in June 2012, the tree had declined further and had began to wilt and turn a dull olive-green which indicated to us the development of the disease With an understanding of it’s mode of attack, it was evident that it would be difficult to retrieve the tree.
Diplodia Blight is an opportunistic and latent pathogen that kills current-year shoots, major branches, and ultimately entire trees. Trees that are pre-disposed by adverse environmental conditions or mechanical damage are more susceptible to infection. Diplodia Blight is one of the most severe and ubiquitous diseases of pine plantations in Australia (Coops N. C., Goodwin N., and Stone C., 2006).
The effective control of this disease requires a predictive process in order to know that the fungus is firstly present and that the condition of the tree in combination with the prevailing weather conditions are conducive to infestation.
Knowledge of the aforementioned factors would have been imperative for effective control of Diplodia Blight.
Current forestry and arboricultural monitoring systems are simply not that sophisticated.
The City of Melbourne has implemented all known, scientifically researched measures in an endeavour to arrest the tree’s decline. However, there is no panacea for this malaise and the measures have not been effective. There is no registered chemical treatment for trees infested with Diplodia.
From a tree management perspective the tree cannot be sustained.
Tree decline is often caused by the interaction of a number of interchangeable, specifically ordered abiotic and biotic factors to produce a gradual general deterioration, which can often lead to tree death.
Tree decline predominately involves three sets of factors:
The first set of factors are generally static or non-changing factors such as the climate, the soil type or site conditions, the genetic potential of the tree and the age of the tree. Such factors put a permanent stress on the plant and predispose it to the actions of other factors (Manion, 1981).
The second group of factors is called inciting. These are short in duration and may be physical or biological in nature. Examples of inciting factors are drought, flooding, air pollutants, or mechanical injury. These factors generally produce a drastic injury. The plant attempts to recover but has difficulty because of the predisposing factors.
The third group of factors are called contributing and are generally the final group to appear. Pathogenic fungi, wood boring insects, viruses, and mycoplasms produce noticeable symptoms and indicators on the weakened host. These organisms are persistent and are often seen as the cause for the condition of the host. They are better considered as indicators of a weakened host. Eventually the plant dies or is rendered useless as an ornamental tree (Manion, 1981).
During the life of any tree it will continuously and repeatedly encounter an array of stress factors. The predisposing factors push the tree towards stress and decline (The Lone Pine’s age and urban growing conditions). The inciting factors accentuate the stress symptoms of the predisposed trees (Prolonged period of drought, removal of large limbs in 2005, unusually wet 2011 Spring). The contributing factors (Diplodia blight) will compete for a niche on the weakened and declining tree.
A combination of the aforementioned factors will lead to tree mortality. Tree mortality is not attributable to any single cause. Mortality is more often the result of a combination or series of factors.
The removal of the Lone Pine will sadden members of the community as the tree has significant sentimental value, however sentiment alone will not sustain this tree. The death of the tree will present a risk potential from falling dead branches and debris. The horizontal transmission from mature to young trees sustains the Diplodia Blight inoculum. Consequently, the expedient removal of the tree is logical from safety and sanitation perspectives.
All trees have a finite lifespan and are vulnerable to ageing and disease. In order to maintain safe and aesthetically pleasing landscapes, at some point in time trees need to be removed and replaced.
The memories of the soldiers of Gallipoli that the Lone Pine helped to retain will be sustained by the younger tree to the west and all efforts should be afforded to it so it may maintain that legacy.
The timber from the Lone Pine will be recovered and used as part of a remembrance project.
On a brighter note, another tree propagated from the Lone Pine was planted back in 2006. The young lone pine is doing well and has been treated with a fungicide to protect it from the infection that killed its parent.
Coops N. C., Goodwin N., and Stone C. (2006) Predicting Sphaeropsis sapinea Damage
in Pinus radiata Canopies Using Spectral Indices and Spectral Mixture Analysis. Photogrammetric Engineering & Remote Sensing Vol. 72, No. 4, April 2006, pp. 405–416.
Manion, P.D. (1981) Tree disease concepts. Prentice Hall.
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