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Ecology and Epidemiology

Effects of Initial Population Densities of Heterodera schachtii on Yield of Cabbage and Table Beets in New York State. G. S. Abawi, Associate professor, Departments of Plant Pathology, Cornell University, Geneva, NY 14456; W. F. Mai, professor, Departments of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 70:481-485. Accepted for publication 7 November 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-481.

Relationships between initial population density (Pi) of Heterodera schachtii and total or marketable yields of table beets, direct-seeded cabbage, transplanted cabbage, and sweet corn grown in field microplots were determined in 1975 and 1977. Total and marketable yields of table beets and cabbage (direct-seeded and transplanted) but not sweet corn were inversely correlated with Pi of H. schachtii. A Pi as low as six to nine viable eggs and larvae per gram of soil decreased marketable yields of table beets and cabbage. In 1975, marketable yields of table beets were decreased by 23, 25, 42, and 54% at Pi of 9, 18, 34, and 68 eggs and larvae of H. schachtii per gram of soil, respectively. These same Pis lowered marketable yield of direct-seeded cabbage by 21, 28, 46, and 54% and that of transplanted cabbage by 25, 31, 34, and 42%, respectively. Table beets produced in soil with the greatest Pis were misshapen and of undesirable size, and cabbage heads were smaller and less firm. Also, fibrous roots of table beets and cabbage plants growing in soil at the greatest Pis were discolored and reduced in size. Final population density (Pf) of H. schachtii were affected by the crop grown and also the Pi. Number of cysts remained approximately the same and the number of viable units was smaller in microplots planted to sweet corn, a nonhost. On both hosts, the greatest buildup of H. schachtii occurred at the smallest Pi, whereas the least buildup occurred at the greatest Pi. Transplanted cabbage supported the greatest reproduction of H. schachtii at all Pis. In 1977, significant reductions in marketable yields of both direct-seeded and transplanted cabbage occurred only at the greatest Pi of H. schachtii tested, 12 eggs and larvae per gram soil. Marketable yields of table beets were not significantly affected by any Pi tested.