Influence of Nonhosts, Crucifers, and Fungal Parasites on Field Populations of Heterodera schachtii
Roberts, P.A.; Thomason, I.J.; McKinney, H.E.
Journal of Nematology 13(2): 164-171
1981
ISSN/ISBN: 0022-300X PMID: 19300739 Document Number: 174954
H. schachtii egg number decline under non-hosts was surveyed for 3-4 years at soil depths of 0-30 cm and 30-60 cm in 3 fields in the Imperial Valley, California, USA. In the 2 fields continously cropped to lucerne, annual decline rates were 49 and 63%, respectively, and did not differ between depths. In the 3rd field, cropped to annual non-hosts and fallowed, decline rates of 56 and 80% at 0-30 cm and 30-60 cm depths, respectively, were significantly different. Egg hatch is the major cause of decline. Soil moisture in relation to type of cropping sequence apparently influenced egg hatch and activity of fungal parasites. An interaction matrix is used to assess the importance of biological, environmental and management factors affecting decline of H. schachtii egg numbers. The required rotation length to non-hosts for various egg densities can be predicted. In coastal California, inclusion of a winter crucifer crop in the rotation increased H. schachtii egg density up to 2-fold. [AS].