Tag Archives: oak processionary moth

Horse and stable door, cat and bag, caterpillar and eradication programme

I found this lovely bristly caterpillar in the garden a few days ago. I’m not sure whether it was eating the peony flower, or leaves, but it was perfectly posed, including a few morsels of frass.

Caterpillar of Lymantria dispar, the gypsy moth.

The gypsy moth, Lymantria dispar, was once native to Britain, more or less limited to East Anglia, but had disappeared after the widespread draining of the fens during the 18th and 19th centuries. When it re-established itself in the London area at the end of the 1990s there was a flurry of activity trying to control what could potentially be a major forestry pest. In some parts of Europe, and in North America (where it was deliberately released during the 19th century for a putative domestic silk industry), it can cause defoliation of large swathes of trees.

The moth, however, seems to be well-esconced here, and eradication plans have subsided. When I found an adult moth in the Olympic Park near Stratford a few years ago there was some mild consternation from the park authorities, but there is precious little anyone can do unless the gregarious caterpillars can be found early enough and the whole nest of them cut out and destroyed.

I’m not sure where my singleton on the peony came from. There are several very large pear trees in neighbouring gardens and we’ve got an apple. I’ll have a closer look over the next few days. The only time I ever saw the caterpillars before, they were feeding on oak trees at the London Wildlife Trust nature reserve at Gunnersbury Triangle. Here they were creating their characteristic silk trails up and down the trunks, moving upwards in procession to feed on the leaves during the night, but returning, following the silk lines down, to huddle in a great knot on the bark during the day.

Earlier this week a London environmental email group produced several reports of sightings in north and east London. It’s obviously doing well in London.

There has also been a spate of recent sightings of the oak processionary moth, Thaumetopoea processionea, in London. Like the gypsy moth it appears to have colonized Britain very recently, and its caterpillars also move in long lines, follow-my-leader style, but only on oak trees. Again, there has been some activity to try and get the public to report outbreaks so that they can be located and destroyed. I’ve just had a notice of work going on in Catford. Concern is centred on possible tree damage, but also on the caterpillars’ long brittle hairs which contain a venom and which can cause irritation in some people. There is a risk of rashes if the caterpillars are handled, or of eye-irritation or asthmatic breathing difficulties since the hairs break and fragments float in the air.

At the moment there is still an expectation that outbreaks should be reported and attempts made to contain and destroy them.

London has a long history of ‘dangerous’ caterpillars, ever since the serious 18th and 19th century outbreaks of browntail moth, Euproctis chrysorrhoea, caused the local beadle to offer a bounty of 6d per bushel for their silk-strand nests cut from the orchards of Clapham and Battersea. There was a massive bonfire to destroy them. Every so often there is a plaintive warning about the stinging browntail caterpillars from various London borough councils, and warningly titled information sheets are circulated.

I can be fairly blasé about browntails since I seem to be able to handle the larvae with impunity. But my sister suffered many years of tearful eye complaints because she lives on the south coast where the moths and their caterpillars are always common. I’ll expect to come across more oak processionary and gypsy moth caterpillars, and will handle them cautiously when I do.

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