Saturday, 10 October 2015
Knoppers on acorns
Prolific years for oak and beech trees when they produce lots of seed are known as good mast years. It doesn't seem to be a great year for acorns.
Some of them have been taken over by the larvae of gall wasps Andricus quercuscalicis, which cause the tree to produce these knopper galls.
The galls turn brown and fall to the ground, and in spring a female gall wasp emerges and flies to a Turkey Oak tree (it must be Turkey Oak) where she lays eggs on the catkins. These eggs produce both male and female gall wasps, which mate. Then the females lay their eggs on a Common Oak, where the acorns are forming, and the cycle starts all over again.
This species first arrived in Britain in the 1960s and the population surged in 1979, so that there were alarmist reports that our oak trees would never produce acorns again. So don't always believe what the papers say.
You ought to take what I say with a pinch of salt too.