Combine sugar and tapioca, mix well. Add apricots and lemon juice. Toss to coat. Let stand for 15 minutes. Line a 9-inch pie plate with pastry. Trim pastry to 1/2-inch beyond edge of plate. Flute edges. Pour filling into crust.
In a smal bowl, combine flour, sugar and pecans. Stir in butter. Sprinkle over filling. Cover edges loosely with foil. Bake at 350F for 15 minutes. Remove foil. Bake 25-30 minutes longer or until crust is golden brown and fillling is bubbly.