Miners in Moreton Hall
Miners are usually people who crawl around in coal seams, sandwiched between layers of rock. In Moreton Hall, there are lots of leaf miners. These are the caterpillars of various moth species, who hatch out from an egg laid inside a leaf. Sandwiched between the top and bottom layers of the leaf, they crawl around mining out (and eating) the soft juicy leaf insides. And as well as only eating the juiciest part of the leaf, they are protected from practically all insect and bird predators. Many species of tree and shrub are used by leaf miners, as many gardeners will know. One species of leaf miner is the imaginatively named Horse Chestnut Leaf Miner, which was first foundin the UK in 2002 and reached Moreton Hall roughly fie years ago.
In the last fie years, since the Horse Chestnut Leaf Miner colonised us, horse chestnut trees have been heavily used by the moth. Most horse chestnut leaves were heavily mined by early September, with most of our horse chestnut trees looking brown and autumnal many weeks before other trees. The leaf miner does not kill the trees, but tree growth is slowed with fewer and smaller conkers being produced The caterpillar pupates as the leaves fall off the trees, and overwinters in the dead leaf where it is safe from predators and insulated in piles of leaves. Next spring, the adult moths will crawl out and start laying again. In the early days, it was advised that every horse chestnut leaf was raked up and burnt, to stop the leaf miner spreading. This is now impractical, so we will be living with this fascinating little beast for decades to come.
