Knopper Galls

Friday, 27 October 2017

We often spot these little structures on our Oaks, but are unaware as to what they are or where they came from. Oak galls are small structures that encase the larvae of a wasp, and come in many shapes and sizes.

The 60’s brought many things to the UK, including Knopper wasps which in turn created these bizarre structures. Oak galls are not known to have any detrimental effect to the host tree, however Knopper galls are slightly different, the acorns, with these particular galls, become disfigured.

Around this time of year, the galls begin to fall. Next spring, the wasp larvae will begin to pupate and work its way out from the vents in the gall. Their first stop, when airborne, is to locate another oak to lay eggs on, before moving on to live their best life.

In the late 70’s there was a significant boom in the population of Knopper wasps, which has impacted the number of viable acorns being produced from these magnificent trees. Despite this, the National Trust has advised that there has not been a substantial impact on the oak population, but they continue to monitor populations should there be future issues.