28th September 2014

Oak Trees are host to 30 different types of gall wasps and you may have been seeing these strange growths in the trees or under them recently -in fact, on our Oak there seem to be more acorn-cups distorted by these than have matured as acorns this year- good news for the parasitic wasps that cause these ‘Oak Nuts’ or, more accurately ‘Knopper Gall Wasps’. Like other galls (e.g. Oak Apples, Oak Marbles– which we used to call Oak Apples!) they do not usually harm adult trees much but they can drastically reduce the Acorns for food for Jays etc in years like this. The larvae that hatch from eggs laid in the

A few of the already hatched gall cases- you can see the acorns have failed to develop, and the hole left by the emerging Wasp.

A few of the already hatched gall cases- you can see the acorns have failed to develop, and the hole left by the emerging Wasp.

A Robin's Pincushion, the growth of the Gall Wasp that lays its eggs on the Dog Rose.

A Robin’s Pincushion, the growth of the Gall Wasp that lays its eggs on the Dog Rose.

forming acorn emerge as tiny Wasps from

An acorn distorted by the Knopper Gall Wasp

An acorn distorted by the Knopper Gall Wasp

 you can see the hole they have emerged from in the photo’s. The Robin’s Pincushion is a Gall of several larvae that each have a chamber inside the ‘Pincushion’. These are quite common on their hosts, Wild  (Dog) Roses at this time of year. They larvae feed on the host plant through the winter and then emerge as adults in spring. They reproduce by Parthenogenisis, not needing a male, and the cycle starts again. Conditions: Yet another still, dry and mostly sunny day in this incredible late summer spell. Temperature: Max 21- Min 14 C.

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