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305 Damage extent

Dictionary: d_extent

The extent of the damage indicates the portion (%) of affected leaves/needles, branches or stem due to the action of the causal agent or factor.

Damage to the branches is expressed as percentage of affected branches, damage to the stem as percentage of the stem circumference.

The extent of symptoms reflecting defoliation (e.g. leaf damage by defoliators) indicates the percentage 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 percentage 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.

For foliage and branches quantification of symptoms is referring to the assessable crown.

The affected leaf area is expressed as a percentage of the actual foliage in the assessable crown 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 %;

  • 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).