The effects of flooding sandy soil on (Para) Trichodorus nematodes as vectors of tobacco rattle virus (TRV) were tested under various laboratory conditions. Few nematodes (viz. T. similis, T. sparsus and P. pachydermus) survived flooding periods of 16 weeks or more. Survival of nematodes was generally not affected by different water percolation rates, by alternating flooding with non-flooding periods or by different daily temperature regimes. Fumigating soil over a 14 day period with hydrogen-sulphide gas (H 2 S) had no clear effect on nematode survival. Effects of flooding on soil infestation with TRV, determined by infection of bait-plants with TRV, did not reflect the decrease in trichodorid nematode numbers. Thus, a near total kill of trichodorid vector nematodes is necessary to substantially decrease soil TRV infectivity which, under field conditions, is unlikely to be achieved solely by flooding.