Conker trees in England are under attack from an alien invader – otherwise known as the horse chestnut leaf-mining moth. The insect, which burrows through the leaves of the trees, first arrived in London from the continent back in 2002. It has since spread to almost every corner of the country, leaving a trail of significant damage in its path. The moths, belonging to the Gracillariidae family, cause the leaves to turn brown, shrivel and fall early.
There is no evidence to suggest the damage inflicted by the insect leads to tree death, although seed weight, photosynthetic storage and reproductive capacity may be reduced. Most trees, however, manage to survive repeated infestations and re-flourish as normal the following year.
Experts had hoped tiny parasitic wasps that lay their eggs in the moth caterpillars would act as natural pest controllers. But it appears the horse chestnut leaf-mining moths are winning this battle, with the latest research revealing the wasps are being outnumbered. The evidence comes from records of leaf damage collected by thousands of volunteers across England over the past few years.
