Tuesday, 21 June 2016

An evening stroll, with postscript

Stand by for a tediously boring blog.

Geum urbanum is known as Wood Avens and indeed I commonly find it growing in wooded areas. But it could equally be called Garden Avens because in cultivated areas it can be an unmitigated nuisance.

Its flowers are small and undistinguished and the plants is generally straggly. The leaves are unremarkable, barely meriting a second glance - usually. This evening however, when out for a constitutional, I did pause awhile to examine a leaf.
The flowers of Wood Avens are only about 7-8 cm across
Christchurch Drive, Daventry. 21 June, 2016
It was grotesquely puckered and discoloured having been attacked by a mite, Cecidophyes nudus. I sense the confusion among my readers: 'Surely it is Eriophyes nudus?' I hear you say. In fact the name I have used seems to have replaced the earlier one.

Wood Avens leaf affected by Cecidophyes nudus.
Christchurch Drive, Daventry. 21 June, 2016
Wood Avens is sometimes known as Herb Bennett; this is derived from herba benedicta - blessed herb. It is regarded as valueless today but my old herbal states: ...Astringent, styptic, tonic, febrifuge, (and) stomachic...Also useful in diarrhoea, sore throat and leucorrhoea. It would surely be easier to list those ailments for which it is valueless. If all that were not enough, it seems the roots were once use to impart a clove-like flavour to ale.

I weed it out whenever I see it.

Be that as it may, I continued my stroll, only to find a vaguely similar situation with regard to a hawthorn bush.
This hawthorn leaf has been attacked by the fungus,
Taphrina crataegi. Badby Road West, Daventry.
21 June, 2016

Should it be regarded as a gall? Probably. It is the work of a fungus, Taphrina crataegi, and this particular plant was badly infested. Serious infestation or not, I have to admit that it is not a situation likely to cause excitement. I moved on.

Another shrub under attack was a nearby blackthorn. The leaves were disfigured by off-white pustules and were caused by a mite, Eriophyes similis. More often these pustules are clustered along the leaf margin but they can be almost anywhere on the leaf. It is exceedingly common.
The pustules of Eriophyes similis on blackthorn.
Badby Road West, Daventry. 21 June, 2016

From pustule to leaf mine...

This Smooth Sow Thistle, Sonchus oleraceus, is much troubled by a species of Chromatomyia but to establish which of the two possible suspects is the culprit I would have to catch a male and examine its genitalia. Life is too short. I must be content with calling it Chromatomyia 'atricornis'.

Smooth Sow Thistle mined by Chromatomyia 'atricornis'.
Badby Road West, Daventry. 21 June, 2016
If you have managed to read thus far you have my congratulations. I'll try harder next time!

Postscript  A flower bud on a plant of elder seemed to have failed to develop properly, instead forming a gall-like structure. I took it home for microscopic examination and found that inside the gall was an orange grub. This is the larva of the fly Placochela nigripes. one of the Cecidomyid flies. Only three records for Great Britain are shown on the NBN Gateway map for this species. This suggests that is very rare yet in fact it is probably quite common - but few people ever look for it.

E-mail Tony White: diaea@yahoo.co.uk

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