2014 has been a wonderful year for blossom, in streets, in gardens and in the countryside. Who can forget this year’s cherry blossom on the Grove – first the pink, then the white and, on a train journey down to London in April, I was entranced by hedgerows piled with may blossom like clotted cream. Even the most modest flowerers have attracted attention; in fact I have been asked by several friends to identify one in particular. It’s a shrub or medium-sized tree, actually quite common in our woodlands, but this year made notable by the profusion of its creamy-white flowers spikes, a member of the Prunus family – the bird cherry. True to its name, its flowers are followed by small black, bitter- tasting fruit – enjoyed by woodland birds.
Walking through Strid Woods in early May, we stopped to admire a particularly fine specimen growing close to the path. Then my husband noticed something else. One of the flower spikes was entirely enclosed in a rather grubby-looking grey web. We continued our walk more concerned with admiring bluebells and listening for warblers than thinking about one tiny twig on one small tree. We should have known better!
Then, last week, a friend e-mailed me a question and a photograph of a small tree in Strid Woods, flowerless, leafless, and swathed completely in what looked like grey webbing. Inside the web, cleverly protected from predating birds, were lots of small, sandy-coloured caterpillars. What were they and what was going on? The answer – an infestation of the caterpillars of the bird cherry ermine moth. The caterpillars spin sheets of silk into a protective cover and then proceed to strip the tree of leaves and buds. I remembered once, in Grass Wood, seeing a whole group of trees similarly infested, a sinister and ghostly sight. Apparently in Bradford in 2011 a whole park-full of bird cherries was attacked, causing considerably consternation among local people.
Luckily the Council decided to let nature take its course and, once the caterpillars had successfully pupated, the weather cleared away the clinging webs, the trees even put on new leaf and put in some good photosynthesising time before the summer ended. Bird cherries and ermine moths have co-existed for a very long time. It is never a good idea for any species to kill off its host!