Seldom are healthy trees removed, but when they are the residue of the bole and root system are still alive but committed to death, when their starch reserves run out. The biological process continues within the cells, they respire and defend themselves, actively fighting off pest and pathogen. As the residue of the tree runs out of energy, the pest and pathogen levels build until the entire host food is exhausted. At this stage there are two courses for these pest and pathogen pressures to take:
- Actively seek out alternate hosts to provide further sustenance, See – Visualising the tree death process or,
- Return to background levels.
Often further food sources are provided in the form of new plantings. Otherwise healthy trees are planted in soils that are carrying heavy loads of pest and pathogen. This may kill them immediately but more often the tree is stunted with low vigour, dying one or two tree years later.
As adults, most understand that food poisoning organisms are everywhere and we eat them all the time – it is just that they are at background levels. However, we also know that food improperly stored will build these organisms to toxic levels. These toxic levels occur long before there are obvious signs of mould growing on the surface of the food. Eating such food will make you very ill or can kill you. With this example we can see it is not the organism itself that is the problem but rather the dose – quantity, of the organism that is consumed that is the problem.
For plants and animals alike getting sick or not is a numbers game:
- Low numbers – Very low host response, little energy requirement from host,
- Medium numbers – Higher host response, greater energy demand to protect host,
- High numbers – Major host response, very large energy demand that may kill host.
Remember the important fact – the only way a plant dies is through starvation, it runs out of food – Starch Energy.
This is why planting site hygiene is so important for both existing and future trees. The removal of any tree must also require the removal or fragmenting of the below ground level residue of the tree. The issue is the integrity of the stump and roots that provide the long-term supply of food for the pest or pathogen. When left entire, there is a very small surface area on which the pest or pathogen can operate. However, once a food source is colonised by a pathogen, that pathogen will defend that food source vigorously, thereby preventing other benign organisms getting much, if any, access to the energy resource. This allows the pathogen to build and grow in mass (size) and in the pressure, it can exert on otherwise healthy plant systems within its reach. Grinding the bole and chasing out the major roots of the tree for at least two metres will segment the tissue into small chips. This dramatically increases the surface area of the tissue allowing a wide range of organisms to colonise these small chips. Each chip only has a small reserve of energy to feed the pest or pathogen and each chip is a separate colony. In this way, the opportunity for one dominant pathogen to develop is avoided. This will see a wide range of beneficial pathogens colonise the segmented mass with the end result that they counteract each other back to substantially a background effect.