Birch dieback

In an event in the Eastern United States and Canada in the 1930s and 1940s, no causal agent was found, but the wood-boring beetle, the bronze birch borer, was implicated in the severe damage and death of the tree that often followed.

In similar crown dieback occurrences in Europe several decades later, the pathogenic fungus Melanconium betulinum were found in association with affected trees,[1] as well as Anisogramma virgultorum and Marssonina betulae.

[2] Birch dieback tends to attack trees that are under stress, such as from drought, through winter kill or exposure to phenoxy herbicides used to control broad-leafed weeds in cereal crops.

In 2015, Stephen Cavers of the Centre for Ecology and Hydrology in Scotland, said "There is a clear increase in the number of novel pests and pathogens affecting the trees and forests of Britain.

Most likely accelerated by the combined effects of, among other things, globalised trade, a changing climate and the planting of exotic species, the checklist of known threats has recently described an exponential growth pattern.