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Further details about each site including origin of the plants and year of planting are supplied in Tables 1 and 2. Site details are: (1) Wooler, Northumberland; (2) Bickleigh, Devon; (3) Swadlincote, Derbyshire/Leicestershire border; (4) Framlingham, Suffolk; (5, 6) two sites both near Reepham, Norfolk. Site details are: (1) Wooler, Northumberland; (2) Bickleigh, Devon; (3) Swadlincote, Derbyshire/Leicestershire border; (4) Framlingham, Suffolk; (5, 6) two sites both near Reepham, Norfolk.
To gather evidence of how long symptoms of ash dieback might have been visible on each site, all six sites were surveyed in detail in 2013.
As a result, more findings were made including a small number of trees on sites where ash had been planted up to five years earlier, providing evidence that some trees had been infected prior to planting out (Sansford, 2013).
It identified a total of 184 infected sites; 114 in the wider environment and 55 associated with recent plantings plus 15 nursery sites (Clark and Webber, 2017).
For each site outside East Anglia, a wider 1.5 km radius survey was also undertaken, to ascertain extent and distribution of symptoms in the wider environment.
Efforts were made to look for factors that were indicators of longstanding disease including widespread dieback, tree mortality, presence of lesions at the tree collar often referred to as basal lesions (Husson in the form of diamond-shaped cankers on the main stem was recorded (i.e. Any dead trees with visible cankers were cut close to the base to reveal the stem cross-section and a count was made of the number of annual rings by eye, to establish an estimated year of death using the known planting date for each site.
Resources limited the number of sites that could be studied but two categories were defined: (1) Sites located in areas of established and widespread infection (in eastern England) and (2) sites geographically isolated from areas of established and widespread infection.
Additional criteria for site selection were: each had a significant component of ash planted in blocks or groups; comparability in age and accessibility; a planting date before 2012; and a geographic distribution which gave national representation.Additionally, aerial photographs of each site from spring/summer 1999 were visually analysed for verification.