|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.|