Wednesday 28 July 2010

Clouds of Horse-Chestnut Miner

The Horse Chestnut Miner (Cameraria ohridella) is a tiny, 5 mm moth whose larvae feed in the inside of Horse Chestnut leaves. This tree is native from the Balkans and it is there, on Macedonia, where the moth was first found in the late seventies and later described as a new species, although it is not thought to be native from Europe. From there the moth has spread to the rest of Europe, wherever Horse Chestnuts are cultivated. The first infestation in the UK found in 2002 in Wimbledon and since it is steadily spreading North and now reached Scotland. The mining larvae cause characteristic brown blotches on the tree leaves, which grow in length but are restricted to the space between main veins. Damage differs quite a bit between trees, but even those quite affected by the miner seem to recover the next season and the miner does not seem to transmit any tree illnesses.

A typical blotch in close-up and...
...a larvae extracted from its leaf
Lightly affected leaves on the first of July
Heavy infestation on mid july
A heavily infested tree
A few specks on leaves of a lightly infested tree.

Yesterday morning and today I passed underneath a heavily infested horse chestnut. There was a cloud of miner moths flying about, then stopping briefly on a cotoneaster underneath. Both days, the moths were not as obvious in the afternoon. I wonder if they form mating swarms, although I haven't found any information on it, despite many years of research into the mating pheromone and ways to control them.

There is currently a survey on to follow the moth spread across the UK and monitor the levels of infestation and the level of natural control by parasitoids. It is very easy to enter data about your local conker trees and the website is here.

1 comment:

Antje said...

That's pretty cool. I did see some infected trees a while back, but it doesn't seem to be that bad this summer.