Gaeumannomyces graminis is pathogenic on many members of the Poaceae family, but is most commonly a problem on wheat, barley, rye, oats and turf grass. G. graminis var. tritici is the form of the fungus that attacks wheat and related species, whereas G. graminis var. avenae attacks oats and G. graminis var. graminis is problematic on turf and other grasses. Since the pathogen takes all of the grain and leaves an obvious ‘white head’ that is empty of seed, the disease it produces is commonly known as Take-all.
This pathogen has a worldwide distribution under temperate conditions or in dry areas where irrigation is used. Take-all development is favored by moist, cool soils ranging from 12° to 20°C. Severity of take-all is increased where alkaline, poorly drained, compacted soils are present. Soils deficient in nitrogen, phosphorus, and/or copper can increase disease severity. These conditions are present in the Pacific Northwest of the US, but the disease occurs in other parts of the US as well.
G. graminis has a wide host range within the Poaceae family. Winter wheat is one of the major hosts for the pathogen, and it occurs wherever winter wheat is grown. The disease is most common where wheat is grown continuously or without adequate rotation, but it can occur in wheat the first year out of sod.