Worcestershire Record No. 21 April 2007 pp. 13-14

John Partridge with guidance from John Meikljohn

Walking on Walton Hill (Clent Hills) in the summer I found that some of the smaller oak trees near the top were very heavily galled; others lower down had galls, but not to the same extent. Talking about this to John Meiklejohn, he observed that these local concentrations were not uncommon, and he wondered whether older trees built up some sort of resistance.

The same trees on Walton Hill had almost every acorn galled by Knopper Gall; some of these were particularly noticeable because exposure to the sun (presumably) had caused them to change colour to a deep red/brown.

In conversation with John Meikljohn he told me that these arrived in force in Britain in 1971. Harry Green then guided me to an article in The British Oak. This article suggest that it first arrived in the 1960s, but expanded greatly from 1971 onwards, starting in Devon and following the prevailing wind through Gloucestershire and over to Norfolk. The same article reports that the sexual stage of the life-cycle appears on Turkey Oak.

John Meiklejohn has also commented on the almost complete absence of spangle galls Neuroterus quercusbaccurum from our oak trees this year; a situation that he can remember occurring back in 1990. This is recorded in a Stop Press insert to Cecidology Vol. 5 No. 2 from Autumn 1990, and the beginnings of the recovery in Cecidology Vol. 7 No. 2 from Autumn 1992. It seems that it took about three years to recover the normal abundance.