- The advancing front - areas recently invaded by the beech scale that are characterized by forests with many large, old trees supporting scattered, sparse, building populations of beech scale.
- The killing front - areas that are characterized by high populations of beech scale, severe nectria attacks, and heavy tree mortality.
- The aftermath zone - areas where heavy mortality occurred at some time in the past and that are now characterized by some residual big trees and many stands of small trees, often of root-sprout origin. In the aftermath zone, young stems are often rendered highly defective through the interactions of established populations of beech scale, nectria fungus, and another scale insect.
|Mature beech scale insects (about 1 mm long). The wax was removed before the photograph was taken.|
|Beech scale nymph (about 0.3 mm long).|
|Sexual fruiting bodies (perithecia) of N. coccinea var. faginata (about 0.3 mm in diameter).|
|The asexual stage of Nectria. The white tufts of spore-bearing branches can be mistaken for isolated colonies of the scale. T|
|Heavy infestations of beech scale can cover tree boles with white wax.|
|A slit flux or tarry spot exudate on a tree that also bears isolated colonies of beech scale covered with woollike wax.|
|Large areas of bark reddened by nectria fruiting bodies.|
|The death of long strips of bark results in serious defect when underlying wood is invaded by insects and decay fungi.||The craterlike scars indicate where small, isolated nectria cankers were walled off by callus tissue. Since most of the cankers did not penetrate to the sapwood, little damage has occurred.|
|Beech snap occurs when wind breaks of trees where wood borers and decay fungi weaken the wood beneath scale-Nectria-killed bark.|
|The beech tree with the ribbon is free of beech scale and Nectria; the tree on the right is severely diseased. Recent trials have shown such clean trees to be resistant to the beech scale.|