The larva of the gall midge Wachtliella persicariae causes galls to form on various plants of the Polygonaceae family including Amphibious Bistort and Redshank. The gall takes the form of marginal rolls, usually on both sides of the leaf which become markedly thickened and often spirally or otherwise contorted. Often several leaves at the shoot tip are affected. 

Other species can cause leaf rolls on Persicaria species, but never as thickened. 

Gall  Adult

Where the host plants grow.

Galls occur from July to September.

Widespread and fairly frequent in Britain.

Thought to be fairly frequent in Leicestershire and Rutland.