When replanting citrus nematode-infested soil with susceptible crops, it usually is important to treat the soil with a 1,3-dichloropropene or other type of chemical for control of this nematode (Tylencbulus semipenetrans Cobb). Since the degree of control of the citrus nematode often is unsatisfactory, an effort was made to develop improved and highly effective methods for applying D-D type chemical in the field. The vertical diffusion pattern and efficacy of D-D for control of the citrus nematodes in a number of Yolo loam and silt loam soils were determined. When the D-D was applied at rates of 60, 90, 120, and 180 gallons per acre, 100 per cent of the citrus nematodes in the top 3 to 5 feet of soil frequently were killed. The amount of the chemical applied and the soil type treated affected greatly the degree of control. The effect of placement depth of the D-D in the soil, moisture content of the soil, time of year applied, and of some post-irrigation treatments on control were determined.
