Common Tree Diseases
Under a stressful environment, tree health will deteriorate and easier to be attacked by disease. In normal situation, foliage disease is less significant than root and trunk disease unless a long term and continuous defoliation is caused, as root/ trunk disease affects the transmission of water and nutrient and may be fatal to the infected plant.
Brown Root Rot (BRR)
What is it?
BRR is also called “Tree Cancer”. It is a kind of fungal infection and commonly starts from the root. It could result in rapid health and structural deterioration and may lead to tree failure. BRR is common in tropical and sub-tropical region like Hong Kong, Taiwan, Malaysia, Japan, etc.
Diagnostic method
Early diagnostic symptoms of BRR disease are difficult to detect. Diagnosis of BRR in trees is usually undertaken in three steps:
- Identification of symptoms (e.g. sparse foliage and yellowing of leaves, small leaf size or shedding of leaves);
- Field diagnosis of other signs and symptoms (e.g. presence of adhesive soil particles, mycelial netting and BRR fruiting bodies);
- Laboratory tests.
Control measure
There is no direct cure for BRR infected trees at present. Trees with poor health are prone to be infected. Having a good tree health by proper tree maintenance is the most effective way to prevent BRR.
Proper site sterilization and debris handling are also important in preventing the spread of the BRR.
Sign of Brown Root Rot
Other fungi
What is it?
Fungi decompose the organic matter and play an important role for keeping a healthy ecosystem. In most cases, Fungi are usually not the main cause of tree accident. When handling the fungal problem, the first step is to identify the impact and species of the fungi.
Control measure
Fungicide is one of the effective ways to control the growth of fungi (e.g. Calixin).
Wood decaying fungi
Non wood decaying fungi
Fungi on leaves
What is it?
In most cases, no significant and permanent impact to the tree will be caused. However, if a large extent of dead foliage is observed, there may be some underlying problems in the tree and should consult Certified Arborist for detail assessment and seek advice.
Control measure
In most cases, removal of the infected leaves is already good enough. However, if the infection area is large, the use of fungicide can be considered.
Photos
Bacteria
What is it?
Bacteria cannot cause any wood decay.
Sometimes, the foul smell (generated by bacteria under anaerobic condition) from the severe decay can indicate the location of tree cavity.
Control measure
Keep the wound or tree cavity dry.
