Simon Colmer / Caterpillar larva of Muslin Moth (Diaphora mendica) on Couch grass, Sussex, UK, July

Nigel Cattlin / Common couch grass (Elymus repens) shoots and rhizomatous roots, on black background.

Nigel Cattlin / Common couch grass (Elymus repens) stems, shoots and rhizomatous roots, black background.

Nigel Cattlin / Common couch grass (Elymus repens) shoots and rhizomatous roots, white background.

Nigel Cattlin / Common couch grass (Elymus repens) stems, shoots and rhizomatous roots, white background.

Nigel Cattlin / Common couch grass (Elymus repens) with rhizomatous roots, white background.

Nigel Cattlin / Couch / Twitch grass (Elymus repens) with complex underground root system of rhizomes, a common weed.

Ernie Janes / Tall oat grass or onion couch (Arrhenatherum elatius) grass weeds in ripe wheat crop. England, UK.

Pascal Tordeux / False Oat Grass / Tall Oat Grass / Onion Couch / Tuber Oat Grass (Arrhenatherum elatius) flowers against a blue sky. Picardie, France, May.

Pascal Tordeux / False Oat Grass / Tall Oat Grass / Onion Couch / Tuber Oat Grass (Arrhenatherum elatius) flower, Picardie, France, May.

Simon Colmer / Caterpillar larva of Muslin Moth (Diaphora mendica) on Couch grass, Sussex, UK, July

Simon Colmer / Caterpillar larva of Muslin Moth (Diaphora mendica) on Couch grass, Sussex, UK, July

Simon Colmer / Caterpillar larva of Muslin Moth (Diaphora mendica) on Couch grass, Sussex, UK, July

Simon Colmer / Caterpillar larva of Muslin Moth (Diaphora mendica) on Couch grass, Sussex, UK, July

David Woodfall / Sea couch grass (Agropyrons repens) washed up by high tide, Somerset, England , August 2009

David Woodfall / Sea couch grass (Agropyrons repens) washed up by high tide, Somerset, England , August 2009

Pete Oxford / Sand dunes with Prickly Couch grass (Zoysia macrantha) growing on the beach, North Stradbroke Island off Queensland coast, Australia

Nigel Cattlin / Couch grass (Agropyron repens) flowering plants in ripe Wheat (Triticum aestivum) crop.

Nigel Cattlin / Couch grass (Agropyron repens) flowering plants in ripe Wheat (Triticum aestivum) crop.

Nigel Cattlin / Onion couch or false oat grass (Arrhenatherum elatius) grass weed culms scattered on the soil after rotavation

Nigel Cattlin / Couch grass (Agropyron repens) roots and spreading young underground rhizomes

Nigel Cattlin / Couch grass rhizomes (Elymus repens), dug up from an established vegetable garden and capable of invasive regrowth Berkshire, England, UK.

Nigel Cattlin / Onion couch / False oat-grass (Arrhenatherum elatius) arable grass weed in a wheat crop coming into ear

Nigel Cattlin / Spraying glyphosate pre-harvest herbicide on to control couch (IAgropyron repens) in a ripe wheat crop

Nigel Cattlin / Severe infestation of couch, twitch or quackgrass (Agropyron repens) perennial grass weeds in a strawberry crop

Nigel Cattlin / Couch (Agropyron repens) perennial rhizomatous grass weed infestation in a cabbage crop