Galls – Barnsley Nats

AutumnWatch galls

AutumnWatch Galls. Looking back to AutumnWatch you may remember a sequence of images of galls including this impressive example …

They are the galls of the Yellow Flat-footed Fly (Agathomyia wankowiczii) on the Artist’s Bracket fungus (Ganoderma applanatum). The only recorded example in Barnsley, it was found by Geoff Jackson in 2016 on a felled Horse Chestnut tree in Woolley Bank woods.

The galls start as small warts, growing up to 1cm in height and caused by the fly depositing its eggs in the fungus. Inside each wart is the grub of the fly. Once the grub is fully grown it bores a hole into the top of the gall and falls to the ground where it buries itself into the soil before it pupates to turn into the adult fly. The holes in this example show that the larvae have left the galls. The fly needs this fungus to survive.

Another local gall seen on AutumnWatch was the Diplolepis mayri, another first for Barnsley. [See earlier post]

Catherine tells us that her article about the galls on Barnsley Main has now been published in the British Naturalist Association magazine. Congratulations Catherine!

Diplolepis mayri – a new gall in Barnsley

Annefie spotted an unusual gall when Peter, Annefie and Catherine were enjoying a walk on Barnsley Main Colliery Pit Stack in August.

It was on a dog rose bush and, at first glance, looked like Robin’s Pincushion (Diplolepis rosae). On closer inspection it is a related gall, being caused by a different member of the same family of gall wasps, Diplolepis mayri.

The gall first appears as a small red pimple, growing into green and/or red tiny spheres, 2-3mm in diameter, and covered with short sharp spines.

The short spines of the Diplolepis mayri contrast with the longer, branched hairs of the Diplolepis rosea – Robin’s Pincushion, distinguishing the two galls. In addition, the small galls of Diplolepis mayri cluster together to form a larger mass, the biggest so far found here being 60mm in diameter.

It is usually a species of southern England, and even quite rare there, so it is well out of its usual range. British Plant Gall Society members have provisionally confirmed the sighting – they have taken a sample for hatching which they expect will lead to absolute confirmation.

Catherine and Mark returned to the site and found the gall on several dog rose plants. There appear to be two main areas of galled plants, all confined within an area about 200m long and to a few yards either side of the public footpath.

There are several dried up, brown remains of some galls clearly showing the insect exit holes. These are mainly on the western edge; so the colony must have overwintered and now appears to be spreading slightly east this season.

Cutting a section across an old gall shows the vacated larval chambers, very similar to that formed by the gall wasp in Robin’s Pincushion, and demonstrating their close affinity.
Notes from Catherine.

Galls at Worsbrough

On September 1st , Pat and I found a gall at Worsbrough near Barnsley, which an I-spot user has since identified as the mite Aceria fraxinivora. We have never observed this gall previously, anywhere.

On the same occasion, we spotted a leaf on a Rosa shrub which was infected with either orange galls or a rust fungus. I would be interested for any comments on the cause of this. Arthur