MANUAL Part II Visual Assessment of Crown Condition - ICP Forests

42 II. CROWN CONDITION ASSESSMENTS
The following sources of information provide information for the field observers to facilitate
the diagnosis:
• Tables A2-3 – A2-11 contain the coding system for damaging agents. Especially the
sheets on insects and fungi provide information about specific symptoms caused by a
selection of relevant organisms.
• http://www.icp-forests.org/WGbiotic.htm >> click on Annex 3, provides codes for
the scientific names of causal agents.
• http://www.icp-forests.org/WGbiotic.htm >> click on Annex 4, provides examples,
descriptions and photographs of damage caused by important categories of insects and
fungi.
• http://www.icp-forests.org/WGbiotic.htm >> click on Annex 5, provides a key with
symptoms linked to frequently occurring damage causes. However keep in mind that
these are possible damage causes, other factors may cause similar symptoms.
Diagnosis should always be confirmed by an expert phytopathologist whenever
possible.
Important remark
Tables A2-3 – A2-11 give an overview of some important damaging factors in Europe. At
national level however, important factors may be missing, while others may be less important.
Therefore countries may wish to compose their own national list of damaging agents/factors
and classify these according to the groups and classes of the manual. Reporting to the
international data centre should always be done according to the categories and codes of the
manual.
A2.5.3 Quantification
For foliage and branches quantification of symptoms is referring to the assessable crown.
A2.5.3.1 Extent
The extent of the damage indicates the quantity (%) of the affected part of the tree due to the
action of the causal agent or factor. Damage to the branches is expressed as a % of affected
branches, damage to the stem as a % of the stem circumference.
The extent of symptoms reflecting defoliation (e.g. leaf damage by defoliators) indicates the
% of the leaf area which is lost due to the action of the agent/factor concerned. This means
that the extent should take into account not only the % of affected leaves, but also the
‘intensity’ of the damage on leaf level: physiologically it makes a difference for a tree if 30 %
of its leaves show only some small holes or if 30 % of its leaves are totally devoured.
The affected leaf area is expressed as a percentage of the actual foliage at the time of
observation.
Examples:
• Crown condition assessment results in a total defoliation score of 40 % (including
defoliation by identified causes like defoliators). 20 % of the leaves in the assessable
crown are totally devoured by defoliators extent of defoliator damage = 20 % (class
2 – see A2.5.3.2);
• Crown condition assessment results in a total defoliation score of 40 % (including
defoliation by identified causes like defoliators). 20 % of the leaves in the assessable
crown are partly devoured by defoliators extent of defoliator damage is e.g. 10 %
(in any case < 20 % since the affected leaves are only partially devoured).
updated 06/2006