Crop rotational and spatial determinants of variation inHeterodera avenae(cereal cyst nematode) population density at village scale in spring cereals grown at high altitude on the Tibetan Plateau, Qinghai, China

Abstract

Cereal cyst nematode (Heterodera avenae) population densities were determined in spring cereals after harvest in three high-altitude villages in Qinghai, China in order to examine the effect of crop rotations. Two villages were sampled intensively to allow examination of between-field spatial variation. The previous season’s crop, including fields where two host crops had been grown in succession, did not appear to influence the final nematode density. A high degree of variation in population density and significant spatial variation appeared to be strongly influenced by the occurrence of hyperparasites, thus masking any possible crop rotation effects. Nevertheless, a third of the fields had final egg densities of greater than 10 eggs/g soil, creating a risk of yield loss if an intolerant host was to be grown in the next year. From the findings, it is suggested that future research should focus on developing locally adapted resistant cultivars and examining factors that determine the efficacy of natural biocontrol.