VIEW ARTICLE

The Relationship between Population Densities of Pratylenchus penetrans and Crop Losses in Summer-Maturing Vegetables in Ontario. T. H. A. Olthof, Nematologist, Research Station, Research Branch, Canada Department of Agriculture, Vineland Station, Ontario; J. W. Potter, Nematologist, Research Station, Research Branch, Canada Department of Agriculture, Vineland Station, Ontario. Phytopathology 63:577-582. Accepted for publication 15 November 1972. DOI: 10.1094/Phyto-63-577.

Six vegetable crops were grown in microplots infested with Pratylenchus penetrans. In general, marketable yields were inversely correlated with preplant nematode population densities. Losses in marketable yields of sweet corn and onions ranged from 30% and 14% at a preplant density of 666 nematodes/kg of soil, to 49% and 71% at 18,000 nematodes/kg of soil, respectively. At preplant densities of 6,000 and 18,000 nematodes/kg of soil, the reductions in marketable yields of cabbage, lettuce, cauliflower, and potatoes were 17% and 25%; 18% and 33%; 19% and 59%; and 35% and 43%, respectively. With the exception of potatoes and onions at the 18,000 density, soil nematode populations under all crops at harvest were higher than at planting. Nematode populations in the roots at harvest were positively correlated with preplant nematode densities, except with potatoes and onions at the two highest densities. Largest nematode numbers/g of fresh root occurred at the 18,000 density with cabbage (450/g), lettuce (1,460/g), cauliflower (1,710/g), and sweet corn (350/g); at the 6,000 density with onions (1,230/g); and at the 2,000 density with potatoes (1,320/g).