Crazy Cleavers

Cleavers, or goose grass, is a problem in my garden. At this time of year I need to pull out armfuls to prevent it taking over. But something has gone wrong with it. I noticed last year a few of the plants were distorted. This year about 80% are affected. The leaves twist round like corkscrews and the growing head is more like a flower than the usual straight stiff leaves. I have no idea why this is happening, but I’m looking forward to seeing if they will have flowers and seeds.

EDIT: Since posting this blip I have learned that the cause of this damage is the Galium gall mite, Cecidophyes rouhollahi. It has only recently been observed in New Zealand. (NZ Landcare Research).