Italiano English
Download PDF

Elms, landscape, and lepidoptera in England

Shortly before World War 1, the redoubtable Henry John Elwes opined that "..during the latter half of November, the bright golden colour of the lines of [English] elms in the hedgerows is one of the most striking scenes that England can produce".* Alas, those iconic elms, like the Constable landscapes they complemented, are gone forever. Nor is it only the landscape which has suffered. The elm is host to a wide range of fauna, from the Tawny Owls which preferred the hollows in elm trunks, to over 200 species of invertebrate, not to mention 100 species of lichen.

Some species of Lepidoptera are entirely dependent on elm, and these have suffered greatly as a consequence of Dutch elm disease. A prime example is the White-letter Hairstreak butterfly, Satyrium w-album, now classed as ‘Endangered’ and accorded DEFRA BAP Priority status. The butterfly not only needs elm, but sexually-mature elm. The larvae hatch in mid-March, weeks before the leaves flush, and immediately feed on the flowers, then the seeds, before moving to the leaves in late April. The White-spotted Pinion moth Cosmia diffinis is likewise dependent on older trees, the females only laying eggs on epicormic shoots.

Butterfly Conservation has been assessing disease-resistant hybrid elm cultivars for 14 years at four sites in southern Hampshire. As all are of foreign origin, it was of primary importance to determine their adaptation to the English climate, so heavily influenced by the gulfstream, with its wet winters and cool summers, and geology. A number of cultivars with purely Asian ancestry quickly perished on clay soils waterlogged in winter, meanwhile those of Dutch origin, with the Himalayan Elm U. wallichiana as the main source of disease-resistance genes, were found not to leaf until mid-May, possibly too late to support the White-letter Hairstreak.

 The most promising cultivar to have emerged to date is ‘Morfeo’, raised in Italy by the Istituto per la Protezione delle Piante. Derived from a crossing of the Chenmou Elm from China and a Dutch hybrid of Wych U. glabra and Field Elm U. minor, it not only thrives in the English climate but has a phenology identical to that of the Wych Elm, the native species favoured by the White-letter Hairstreak.

 

 

 

 

 

Some species of Lepidoptera are entirely dependent on elm, and these have suffered greatly as a consequence of Dutch elm disease.

contenuto