On the Specific Status of the so-called Biological Strains of Heterodera schachtii Schmidt

The genus Heterodera comprises three species, the root-knot nematode, H. marioni (Cornu 1879) Goodey 1932, and the two species in which cysts are produced. These are, H. schachtii Schmidt 1871, which is associated with disease in potatoes, sugar beet, cereals, peas and some other crops, and H. punctata Thorne 1928, which has caused disease of wheat in Canada, and has been found in this country infesting a common grass Agrostis stolonifera L.