I have had several messages about this pest which devastates box plants. It has no predators and will quickly eat all the leaves on your carefully tended plants. The weather this year has produced a bumper crop of butterflies and moths, which I've welcomed into my garden. However this unwelcome moth variety appeared to produce it's caterpillars overnight, and they quickly munched their way along my box hedges and my box spheres and pyramids.
The first image shows the difference between my affected and unaffected box plants.
I hate to use insecticides, but I have found a product that only targets Box Tree caterpillars. I thoroughly sprayed the little devils as directed, and 2 weeks later have seen no further evidence. The neighbours must think I'm very odd: peering into my little hedges on a regular basis! As soon as I see any more, I'll spray again.
The plants should recover and already show some signs of leaf growth. I'll be watching carefully!