I’ve often wondered about the oak tree I sit under every day. My studio is directly beneath it. During the day I can hear woodpeckers drumming on the dead wood right at the top of the tree. Blue tits collect insects and sing to claim their patch. Squirrels scurry and leap and there’s an occasional thud on the roof… when twigs fall. I see a flash of blue when the jays visit for acorns. In the evenings I hear tawny owls hooting right above me and the flutter of restless wood pigeons. It’s always full of life. I love to spend a few minutes outside every day to get a glimpse of what’s going on in that tree.

How many creatures rely on English Oak trees for their existence I wonder?

There were hundreds of tiny round seed-like thingys on the path under the oak tree this morning. Closer inspection revealed clusters of these discs not only on the path but also on the fallen oak leaves and twigs. Hmmm… rather like scale insects I thought.

I turned to the RHS for information. Their book on Pests and Diseases is brilliant. Not only does it explain what each pest or disease is… the authors Pippa Greenwood and Andrew Halstead also suggest ways to control it if necessary. And very often it isn’t necessary. In many cases what seems to be a harmful infestation turns out to be a perfectly normal life cycle of a living creature I haven’t seen or heard of before.

It turns out that English Oak Trees are the host plant for over 30 species of gall wasps. They lay their eggs in the leaf buds then the larvae of the gall wasps secrete chemicals which cause the oak tree to produce galls. And that’s what all these little discs are.
For a better view just click on a picture to open the gallery.

Clusters of discs on the back of leaves

Donuts produced by silk button gall wasps

Discs produced by the common spangle gall wasp

Infestations of gall wasps look unsightly but cause no harm

It seems that the common spangle gall wasp is responsible for the discs. The silk button gall wasp has produced the donut shaped galls. Lucky us! O_o  We’ve got acorn gall wasps too. They lay their egg inside developing acorns which feed the larvae and turn into galls instead of acorns.

According to the RHS control measures are not necessary as even large infestations of gall wasps cause little damage to the oak trees they inhabit. Phew! Thank goodness for that. It’s just life going on as usual in the oak tree.

Do you have any interesting pests or diseases in your garden?
I’d love to hear about them.    Gillian