Observations on the prevalence and incidence of cereal cyst nematode (Heterodera avenae) in Scotland

A survey of the incidence of cereal cyst nematode (CCN) in Scottish cereal-producing land showed that 69% of fields contained CCN cysts and of these 54% contained eggs. CCN infestations were more frequent in SE and NE areas. Populations were small despite intensive cereal cropping, 71% having less than 1 egg/g soil and only 3% having more than 6 eggs/g soil. Soil type and cropping frequency were important in influencing the infestation of fields with CCN. Infested fields occurred most frequently in freely draining loamy-drift soils and populations were larger when these infested soils were cropped more frequently with cereals. In the soils that were less well draining, fewer infestations occurred and cropping frequency was less important, although cropping with oats in these soils was associated with larger CCN populations. A survey of seed-potato-producing land showed that 55% of fields known to contain CCN had viable populations but that population densities were smaller than in the more intensively cereal-cropped fields.