Wednesday, 23 September 2015

Oak in the pocket park

Prior to our move to Daventry I would visit Byfield Pocket Park about twice a week; now it is just the occasional jaunt.

However, today I found myself with a spare hour so I decided to take a look. Autumn is now with us and plants are beginning to display an ever-increasing range of evidence that during the summer they have been under attack.

Tar Spot on Acer pseudoplatanus. Byfield Pocket Park.
23 September, 2015

Perhaps the most obvious sign of leaf damage is the black blotches of Tar Spot, Rhytisma acerinum. It is often referred to as Sycamore Tar Spot as it is apparently confined to that species, with Field Maple, Acer campestris, seemingly immune. Though disfiguring it appears to cause no great damage and I suspect that we'll just have to live with it.

Many of the leaves of Blackberry were covered with purple spots, the work of a fungus. It may be Septoria ribis, but leaf spots of this kind are a job for the specialist and I wouldn't presume...

These however were but slight diversions. My main objective was an oak tree in the middle of the pocket park. It isn't very large as oaks go but it is the largest that the site has to offer - and it proved to be of considerable interest.
Knopper Galls, like this specimen, can sometimes take on
red colours. Byfield Pocket Park. 23 September, 2015

Immediately very obvious was this Knopper Gall, Andricus quercuscalicis. This gall, induced by a cynipid wasp, is of course very common but, having taken on this cherry red coloration, it demanded to be photographed.

Acorn Weevil. Quite common but new for Byfield
Pocket Park. 23 September, 2015
It was while examining the acorns that I noticed this weevil. It is the Acorn Weevil, Curculio glandium, found widely in south and eastern England, and I brought it home for a photograph. The remarkably long, curved  'snout' (known technically as a rostrum) enables the female, who has a longer rostrum than the male, to bore into acorns, where she lays her egg. The adult is quite large as weevils go, with this specimen being 7mm long. It is a 'first' for the pocket park.

Andricus aries on, as always, oak. Byfield Pocket Park.
23 September, 2015

Nearby - and slightly out of focus - was this Ram's Horn Gall, Andricus aries. Its 'two-horned' structure makes it instantly identifiable and, although I had once found it in the pocket park as a withered mid-winter specimen, it was even then easy to recognise.

Adjacent to the oak tree were Stinging Nettles, and on them were dozens of little Woundwort Bugs, Eysarcoris venustissima. This was odd for, as the name suggests, the species is normally found on Hedge Woundwort, Stachys sylvatica, a common plant in the pocket park. It has been recorded on other plants such as Horehound and Red Bartsia - but Stinging Nettle?

Woundwort Bug nymph. Byfield Pocket Park.
23 September, 2015

Even odder was the presence, on the same plant, of Woundwort Bug nymphs. However, they did not appear to be feeding. The nymphs are quite unlike the adults.

Roger Hawkins, in his book 'The Shieldbugs of Surrey', notes that the species was rare in that county during Victorian times. The same is probably true of Northamptonshire.

23 September, 2015 and hogweed is still in flower, as it
could be for some weeks yet. Byfield Pocket Park.

Hogweed, Heracleum sphondylium, was still in flower, but only where plants had been cut back in the summer. It was receiving a few insect visitors but when any morning dew has evaporated it will probably attract quite a lot more.

Bedeguar Gall, aka Robin's Pincushion. Byfield
Pocket Park. 23 September, 2015

Some ten feet away a wild rose was bearing two Robin's Pincushions. This is an old country name for the bedeguar gall, a term derived from the Arabic bad-awar, meaning 'wind brought'. Though a romantic idea, the wind has nothing to do with it. The gall is the work of a wasp, Diplolepis rosae, an interesting species which seems to reproduce parthenogenetically, as no males have ever been found.

The gall consists of a mass of rather sticky, filamentous material which contains up to a hundred cells. Each of these will contain a larva of the wasp. Also finding a congenial home there will be a number of inquiline species, with over a dozen identified so far (see my blog for 17 October, 2013). Research continues.

My pocket park visit could not continue however as I was needed elsewhere. But it had been worthwhile and several species were added to the pocket park invertebrate list which now stands at 547 species.

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