This paper investigates the excitation and control of the driven l=1 diocotron mode in a pure electron plasma by adiabatic passage through higher order resonances. The excitation takes place when the driving frequency ωd is swept such that its nth harmonic passes through the linear diocotron mode frequency ω0; ωd≈ω0/n, n=2,3,…. Once past the resonant region, the mode enters the autoresonant regime characterized by persisting phase locking and strong nonlinearities. The transition to autoresonance occurs provided that the driving amplitude exceeds a sharp threshold, which scales as A3/(4n), where A/2π is the driving frequency chirp rate. The theory of these thresholds for n=2 and n=3 is developed and experimental results for n=1,2,3,4 and 5 are presented.