The quiz question is about the loss of trees from the Park Lane horse chestnut avenue over time comparing the number of trees shown on the First Edition Ordnance Survey Map of 1886 with those that one can see today.

The 1886 map is held online by the National Library of Scotland at this link.

The horse chestnut avenue is clearly shown along the side of Park Lane within Long Meadow. The map shows that it continued beside the byway to Westwick within what is now known locally as ‘Chestnut Meadow’.

There are far fewer trees in the avenue today. The cause of the losses is the disease bleeding canker. In recent times the rate at which the trees succumb to this disease has been about one tree every two years. If this rate continues we will soon see the last of these majestic giants fail.

You can find out more about bleeding canker on the Forestry Commission website.

Today the trees in the avenue also suffer from horse chestnut leaf miners. The horse chestnut leaf miner is the larva of a tiny moth. The female moth lays her eggs on newly opened leaves. The hatched larvae ‘mine’ into the leaves to feed on them. The mature larvae pupate and can overwinter in the leaf litter. The first horse chestnut leaf miner record in the UK was in 2002, having spread across western Europe from the Balkans (which is also the natural range of the horse chestnut).

The horse chestnut leaf miners which are present in huge numbers cause the leaves to turn brown and fall early. There is no evidence so far to suggest that this harms the tree, as most of the damage occurs late in the season, but it does affect its appearance. However many years of leaf miner infestations can leave horse chestnuts weakened. This can leave the trees in a vulnerable state where they are more susceptible to diseases like horse chestnut bleeding canker.