Movement of Pratylenchus Penetrans and the Moisture Characteristics of Three Ontario Soils 1)

Abstract

The movement and survival of Pratylenchus penetrans were studied in three soils, Fox loamy sand, Jeddo loam, and Vineland silt loam that had marked differences in particle-size distribution, moisture retention, aeration, and pore size. Nematodes on paper disks were placed on the surface of soil cores that had been packed to two bulk densities and equilibrated at eight moisture regimes. After seven days the cores were partitioned, the nematodes extracted and counted. At low bulk density, a percentage of 4th and adult stages moved 4 cm in Fox between 10 and 3000 cm H2Ο moisture tension and in Jeddo and Vineland between 30 and 300 H2Ο; a percentage of 2nd and 3rd stages moved 4 cm in Fox between 10 and 100 cm H2Ο moisture tension and in Jeddo and Vineland at 30 and 100 cm H2Ο. However all stages moved only an average of 2.0 cm in Fox at 10 cm H2Ο moisture tension and in Jeddo and Vineland at 100 cm H2Ο. At high bulk density, a smaller percentage of all stages moved 4 cm only in Fox at 30 and 100 cm H2Ο moisture tension and in Jeddo at 100 cm H2Ο. Moreover 4th and adult stages moved only an average of 1.0 cm in Fox, 1.3 cm in Jeddo and 0.5 cm in Vineland at 100 cm H2Ο moisture tension in each soil; 2nd and 3rd stages moved an average of 1.0 cm in Fox and 0.5 cm in Jeddo at 100 cm H2Ο in both soils. In Vineland 2nd and 3rd stages did not move. Eight to 12 percent of the soil volume was occupied by air when movement of all stages peaked in each soil. It is suggested that the relatively large sand grains in the Fox soil provided pore sizes and moisture characteristics more suitable for nematode movement.