Plant-Parasitic Nematodes Associated with Reduced Wheat Yield in Oregon: Heterodera avenae

Heterodera avenae is widely distributed in the western United States, where most wheat is grown in non-irrigated winter wheat/summer fallow rotations in low rainfall regions. Economic and social pressures have motivated growers to pursue a transition from winter wheat/summer fallow rotation to no-till annual spring cereals. Annual cereals are also planted in some irrigated fields. The impact of H. avenae on spring wheat yield in the Pacific Northwest had been observed but not quantified. Spring wheat was planted with or without aldicarb to examine relationships between H. avenae and yield under dryland and irrigated conditions in moderately infested fields. Spring wheat yields were negatively correlated (P < 0.05) with initial populations of H. avenae. Aldicarb application improved spring wheat yield as much as 24%. The infective juvenile stage of H. avenae reached a peak density during mid-spring. Yield of irrigated annual winter wheat was also negatively correlated with initial density of H. avenae. Research priorities necessary to develop control strategies include a description of the pathotype, identification of sources for genetic resistance, and integrated practices designed to manage multiple yield-reducing pests.