caterpillars on parsnip foliage

[Anne Wood]

If you have thin brown papery patches on your parsnip leaves. I am afraid the caterpillars have started munching, they seem to eat away all the green matter underneath the leaf, just leaving the upper layer. But Willsandlands who has commented on this blog ” how to keep caterpillars off my brassicas” suggests a biological control and has left the web site address. I have ordered some immediately and am hoping this will be the answer.