Wednesday, 2 May 2012

About the moth 2

Where has it come from?

The horse-chestnut leaf-miner was discovered in the Balkans (near Lake Ohrid in Macedonia) in the late 1970s. It was then discovered in Austria and from these two focal points, the moth has spread rapidly throughout Europe.

The spread of the moth in Britain

The spread of the horse-chestnut leaf-miner. Data from Forest Research

Thanks to the efforts of Nigel Straw and Christine Tilbury at Forest Research, we have a good record of the spread of the moth since its arrival in west London in 2002.

It has spread quickly through Britain, so that by the end of 2011 it was widespread south of the Pennines. Its distribution in south-west England and Wales is patchy than elsewhere in sourthen England, this is probably due to the smaller number of horse-chestnut trees in these area and that the leaf-miner has only recently arrived in these regions.

How quickly does it spread?

Studies across Europe suggest that the moth spreads at an average rate of about 30km per year.

How does it spread? 

The moth can spread by flying. It is a very small moth and probably is a weak flier. However there can be so many adult moths emerging from the leaves of an infested tree that just by chance a few inidividuals may manage to travel a mile or two.

The main way in which the moth spreads long distances is probably by 'hitch-hiking' on vehicles. Our anecdotal evidence supports this notion. A couple of years ago I was looking round a south Devon coastal town for the horse-chestnut leaf-miner and the only place I found it was in the car park of a holiday resort, suggesting it had hitch-hiked with holiday-makers. A few months later I was photographing a horse-chestnut tree, then walked back 20 metres, got in the car and discovered several of the moths had come in the car with me.

Thanks to Forest Research for allowing us to use their distribution data in the Conker Tree Science project.

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