The upper and lower critical points are investigated in untwinned YBa 2Cu 3O 7−δ single crystals with dilute columnar defects. Dilute columnar defects raise the upper critical point, indicating that the transition near the upper critical point is a vortex entanglement transition. The lower critical point is very sensitive to columnar defect disorder and its position can be described by a Lindemann-like criterion similar to that for melting. Dilute columnar defects induce non-linear behavior in the I-V curves of the vortex liquid state above the lower critical point, which we interpret as a vestige of the critical region associated with the Bose glass transition below the lower critical point.