# Commission Regulation (EC) No 1737/2006 of 7 November 2006 laying down detailed rules for the implementation of Regulation (EC) No 2152/2003 of the European Parliament and of the Council concerning monitoring of forests and environmental interactions in the Community, Division (91): Extent

Extent: E+W+S+N.I.

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, e.g. the % of affected branches.
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.

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Source: https://www.legislation.gov.uk/eur/2006/1737/annex/I/chapter/15/division/13/division/91 (the official version)
Page: https://openlegislation.uk/eu-regulation-2006-1737/annex-I/chapter-15/division-13/division-91
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.