Aceria tenuis is a gall mite that causes phyllanthy on Cock’s-foot (Dactylis glomerata) and various other grasses. The mites live in the length grooves of the grass leaves; on grasses with smooth leaves they are much less numerous. At high densities rolling and withering of the leaves does occur, also growth disturbance, malformations and discolouration of the inflorescence.

Gall Adult

When recording the gall caused by Aceria tenuis please provide a photograph in support of your record and in the comments name the host species.

The galls may occur wherever the host grass species are found.

Summer and autumn.

True status in Britain is difficult to determine due to lack of records.

Rarely recorded in Leicestershire and Rutland.