Biological soil disinfestation (BSD), involving incorporation of grass combined with plastic mulching, eliminates many soilborne pests and diseases through the creation of anaerobic conditions. BSD was compared at two locations with a nontreated control. Italian ryegrass amendment alone, and plastic mulch alone. After the soil treatments, plots were cropped with Acer platanoides and Catalpa bignonioides and grown for 4 years. Relative to the control, soil inoculum levels of Verticillium dahliae were reduced by 85% after BSD and did not increase for 4 years. Populations of Pratylenchus fallax, known for their interaction with V dahliae, in the soil and in roots were reduced by 95 to 99%. The incidence of infection by V dahliae was reduced by 80 to 90%. Verticillium wilt severity was significantly reduced in A. platanoides in all 4 years at one location and in the first 2 years at the other location, and significantly fewer plants died at one location. Shoot length and trunk width were larger after BSD compared with the control at one location. Market value of the crop in BSD plots was up to E140,000 ha(-1) higher for A. platanoides and up to E190,000 ha(-1) higher for C. bignonioides than in the untreated control. BSD is an effective, economically profitable, and environmentally friendly control method for tree nurseries.