Niche distribution of Paratrichodorus minor and Belonolaimus longicaudatusfollowing fumigation on potato and cabbage

An experiment was conducted to determine population changes and niche Varia tion in the soil at two depths (0 to 20 cm and 20 to 40 cm) of Paratrichodo rus minor and Belonolaimus longicaudatus populations following fumigation. Eight plots each of potato (Solanum tuberosum) and cabbage (Brassica olerac ea var. capitata), fumigated with 1, 3-dichloropropene or nonfumigated, wer e established. Eight plots of sorghum-sudangrass hybrid (Sorghum bicolor x S. arundinaceum var. sudanense) were also used to monitor depth distributio n (0 to 20 cm and 20 to 40 cm) of B. longicaudatus and P. minor following e ach cabbage/potato season. Soil samples were taken 0 to 20 cm and 20 to 40 cm deep during the potato/cabbage, and sorghum-sudangrass growing seasons. During the 1993-94 and 1994-95 potato/cabbage seasons, P, minor was found a t highest numbers at 20 to 40 cm, whereas numbers of B. longicaudatus were highest at 0 to 20 cm. During the 1994 and 1995 sorghum-sudangrass growing seasons, B. longicaudatus numbers were highest at 0 to 20 cm. Paratrichodor us minor numbers were highest at 0 to 20 cm and at 20 to 40 cm deep in the 1994 and 1995 sorghum-sudangrass growing seasons, respectively. Reduction b y soil fumigation of B, longicaudatus at 0 to 20 cm deep did not affect dep th distribution or cause P. mine, populations to increase in potato or cabb age plots. Paratrichodorus minor numbers increased at 20 to 40 cm deep in t he 1994-95 cabbage season after soil fumigation.