A survey of nematodes associated with cereal crops in Spain has been in progress since 1971. From a total of 350 soil and root samples examined to date Heterodera avenae Woll. occurred in 35% of samples from wheat (Triticum sp.), 30% from barley (Hordeum vulgare L.) and oats (Avena sativa L.), and 5% from maize (Zea mays L.) samples; the nematode has never been found in soil collected from rye (Secale cereale L.). From a detailed study of the nematode specimens, some small morphological differences were identified which suggested there were three different types present, named here as A, Band C (Table I); the terminology does not have any relationship with pathotypes. Nematodes in the roots were detected by staining in lactophenol and acid fuchsin. Cysts were extracted from the soil by a Fenwick apparatus. Measurements and descriptions are based on specimens mounted in clear lactophenol.
