Tree planting

We have been making what might seem to our followers like a great fuss about the planting of just a very few disease resistant elm trees. Here are parts of a post from March 2020, which explain what disease our precious saplings are resistant to, and why we are so eager to get them established in the hedge between Cornfield and Sleepers.

Dutch elm disease

Dutch elm disease is one of the most serious tree diseases in the world. It was originally identified in the 1920s in an outbreak that killed perhaps a quarter of Britain’s elm trees. It returned in an even more aggressive form in the 1970s and killed almost all of our mature elms and continues to spread today.

It is caused by a fungus that is carried between trees by several species of beetle of the genus Scolytus that lay their eggs underneath the bark of elm trees. When the eggs hatch, the feeding larvae create distinctive fern-like patterns in the wood just under the bark.

1. Mature elm tree 2. Marks left by elm bark beetle larvae 3. Elm bark beetle

By the late 1980s the bark beetles had infected most of the mature elms that they relied on for breeding sites, beetle populations declined as the trees died and the disease virtually disappeared from many southern and south-western areas.

The elm saplings, suckers and seedlings too young to meet the elm bark beetle’s requirement as sites for egg-laying, survived. The beetle returned, though, to attack this new generation of elms once they were large enough to support their reproductive needs. Treatment seemed impossible, so the focus has been on developing disease resistant cultivars.

White letter hairstreak

White letter hairstreak butterflies are entirely dependent on elm trees. They lay their eggs in the tops of elm trees, their larvae feed there and the adults live there in small colonies.

Dutch elm disease was a disaster for the white letter hairstreak: almost total loss of both habitat and larval food plant. At first, it was believed that the species might become extinct in the UK but colonies have survived among the young trees

4. Adult white letter hairstreak 5. White letter hairstreak egg 6. White letter hairstreak larva.

We hope that there is a colony of white letter hairstreaks in the young elm trees in the hedge at the bottom of Sleepers; they have been seen and reliably identified there. Our disease resistant elms is an attempt to provide long term habitat for these rare butterflies before the Dutch elm disease catches up with and kills the young trees they are presently colonising.

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