Wednesday, 14 August 2013


Everyone knows about the ravages of Dutch Elm Disease and they way in which it wiped out Britain's Elms. Except, of course, that it didn't. Gone are the huge old elms of my childhood, but in the countryside relatively few elms died and certainly around Byfield - and over most of the English midlands - they are still common. Elms grow steadily for a few years, reaching maybe 2 or 3 metres in height, and are once more cut back by the disease. In some places hedgerows of almost pure Elm may be found, and in nearly all cases they consist of a single suckering tree; they are in fact, one clone.
Hedgerow of Elm, Solden Hill, Byfield.
13 August, 2013

Elm leaves mined by (probably) Fenusa ulmi
Byfield. 11 August, 2013

Elms are tricky to identify but in our area they seems to be mostly English Elm, Ulmus procera. In places there are also thickets of Small-leaved Elm, Ulmus minor. In the heyday of Elm many insects were dependent upon Elm and, remarkably, most of these species are still with us. I was reminded of a few days ago when I noticed mines on Elm leaves only 100 metres from my home. The culprit may be Fenusa ulmi (also referred to as Kaliofenusa ulmi) but I am not convinced. If I am right, this is a small sawfly which has been accidentally introduced from Europe into North America, where it is now a pest.

The Elm hedgerow at Solden Hill, shown above, is probably Small-leaved Elm. Ulmus minor subsp. minor. This species is extremely variable, making positive identification near-impossible for the non-specialist. Wherever I have found this species I have noticed that the leaves have been galled by the tiny mite, Aceria campestricola. Often a single leaf will bear dozens of these galls, giving it an odd, scabrous appearance, but they seem to do little obvious harm to the tree. The larger leaved Elms are apparently not affected.

Elm leaves galled by the mite Aceria campestricola.
It may be my imagination but Elms seen to be coping a little better recently with Dutch Elm Disease. I have notice several specimens of English Elm reaching 7 to 8 metres. Eventually they succumb, but it would be wonderful if some are developing a measure of resistance. We have planted one resistant specimen in our pocket park and its progress will be monitored with interest.