Influence of Crop Rotation on Spread and Density of Heterodera schachtii on a Commercial Vegetable Farm in New York. W. F. Mai, Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. G. S. Abawi, Associate Professor, Department of Plant Pathology, Cornell University, Geneva, NY 14456. Plant Dis. 64:302-305. Accepted for publication 24 October 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-302.

On a 43-ha farm with 13 fields studied from 1971 to 1977, host (H) crops in the rotation were cabbage and table beets and nonhost (NH) crops were corn, wheat, and oats. In general, the number of viable eggs and larvae of Heterodera schachtii increased in fields with rotations of NH:H crops at a ratio of 1:2 or 1:1 and decreased in fields with rotations of NH:H crops at a ratio of 2:1 or 5:1. Crop rotation did not stop spread of the nematode from field to field within the farm. During the period of study, the number of fields with detectable nematode infestation increased from six to nine and the number of infested sampling grids within fields increased from 58 to 81. The number of fields having at least one sampling grid infested with H. schachtii at above the damaging level (six to nine eggs and larvae per gram of soil) decreased from four to one, whereas the number of sampling grids with a similar level of infestation decreased from 24 to one.