gutters and ditches in huge quantities. The phenomenon was observed all over England and
from Anglesey in Wales to Normandy and Brittany in France. A noticeable feature of the seed
produced was its viability; most if not all the seeds were reported fertile and germinated freely.
The seedlings at one location, Boyton Hall, Roxwell, were reported to carpet half an acre of
land! What a fascinating experiment it would have been to have let the seedlings develop, to
see how they competed with each other and other species and most importantly to have observed
the morphological variability (or lack of it) of the resulting elms. The ground was, however,
ploughed. Importantly Miller Christy noted elm seedlings growing in a wood (Nightingale's
Wood, Roxwell), evidence that elms, if given the opportunity, are able to establish themselves
from seed in woods.
Dutch Elm Disease
The latest outbreak of Dutch Elm Disease started in Britain in the late 1960s in the Bristol and
Gloucestershire areas. By the early 1970s this particularly virulent strain of the disease was
found, notably, in central south Essex. It went on to destroy, by various estimates, between 11
and 25 million elms in Britain, some 90% of all mature elms. Of the elms in Essex, the English
Elm, so characteristic of the south of the county, was hardest hit. I don't know of any large tree
that has survived the epidemic. East Anglian Elm and Wych Elm were also badly hit but had
a significantly better survival rate than the English Elm. I know of numerous large East Anglian
Elms that have survived elm disease and some clones, those on Dengie for example, are either
more resistant to the disease or less susceptible to attack by the beetle that transmits the disease.
I have also found a number of mature Hybrid Elms that have obviously survived.
The fungal pathogen that has caused the current outbreak of elm disease is an aggressive
strain of Ophiostoma ulmi (syn. Ceratocystis ulmi), which is carried from tree to tree by two
beetles: Scolytus scolytus (syn. S. destructor) and S. multistriatus, the elm bark beetles. The
fungus gains entrance to the tree via the adult beetles' feeding wounds on the bark of the tree.
The spores then invade the water vessels of the tree. The tree responds by producing 'tyloses'
in these vessels which block the spread of the fungus, but also block the flow of sap, which
ultimately kills the target branch of that particular vessel. The branch rapidly dies, the leaves
turning an autumnal yellow, then red-brown in midsummer. The fungus can linger on in the
trunk and roots for many years, eventually killing the whole tree and infecting other trees via
the roots. In many places in Essex English Elms rapidly produced suckers with the death of the
parent tree. The suckers too became infected either via the roots or reached a certain size
favourable to the attentions of elm bark beetle and once again succumbed.
Research (Brasier & Webber, Forestry Commission Bulletin 65,166- 179) has revealed the
existence of at least three strains of Dutch Elm Disease: a long-established (in Britain) non-ag-
gressive form, and American and European strains of the aggressive form. The American type
causing the latest outbreak in Britain, entering the country on imported elm logs, the European
form infecting elms on the continent. Oliver Rackham thinks that Elm Disease has always been
present in Britain, but has not had the devastating effects of the present outbreak. Rackham also
suggests the disease may lose its virulence in time; other scientists doubt the disease will become
less pathogenic.
A recently discovered virus-like disease (the d-factor) which impairs spore germination and
the production of fruit bodies in O. ulmi may have some effect on the future spread of the disease.
For more detailed accounts of Dutch Elm Disease see:
Rackham (1980), pages 257-265
Rackham (1986), pages 240-247
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