Besides being a destructive weed, quackgrass possesses other undesirable characteristics. The plant is often infected with stem rust, a fungus disease of wheat. It is an alternative host of bromegrass mosaic virus. Barley has been damaged by wheat bulb fly larvae in fields where the original infestation was on quackgrass. Species of Ophiobalus and Helminthosporium associated with foot-rot of wheat have been found on quackgrass roots.
Considerable evidence supports allelopathy in quackgrass.
Among other things, decaying quackgrass residues release water-soluble germination inhibitors. Quackgrass is not without virtue. Quackgrass is still planted in Holland to stabilize new dikes. It provides cover for wildlife, including mammals, some song birds and game. In Michigan research, quackgrass was one of the most effective plants for reclaiming nutrients from municipal sewage effluent sprayed on vegetation in abandoned fields.