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Yield Losses in Fall-Maturing Vegetables Relative to Population Densities of Pratylenchus penetrans and Meloidogyne hapla. J. W. Potter, Nematologist, Research Station, Agriculture Canada, Vineland Station, Ontario, L0R 2E0; T. H. A. Olthof, Nematologist, Research Station, Agriculture Canada, Vineland Station, Ontario, L0R 2E0. Phytopathology 64:1072-1075. Accepted for publication 29 January 1974. DOI: 10.1094/Phyto-64-1072.

Commercial cultivars of fall-maturing red beets, lettuce, and spinach were grown in microplots infested with either lesion nematodes (Pratylenchus penetrans) or root-knot nematodes, (Meloidogyne hapla) at 0, 666, 2,000, 6,000, or 18,000 nematodes/kg of soil. Yields of marketable product tended to be inversely correlated with preplant nematode population densities. With P. penetrans, losses in wt of marketable produce at the highest preplant density were: beets, 27%; lettuce, 43%; and spinach, 21%. With M. hapla, comparable losses in wt of marketable produce were: beets, 22%; lettuce, 81%; and spinach, 13%. Soil populations of P. penetrans were higher at harvest than at planting under lettuce, about equal at planting and harvest under spinach, and lower at harvest than at planting under beets. Soil populations of M. hapla larvae were lower at planting than at harvest for all three crops; all crops were galled, lettuce more severely than spinach or beets. Beet is recommended as a fall-maturing crop in soils infested with up to 6,000 P. penetrans or M. hapla/kg soil.