  We study the effect of dephasing on the coherent dissociation dynamics of an
atom-molecule Bose-Einstein condensate. We show that when phase-noise intensity
is strong with respect to the inverse correlation time of the stimulated
process, dissociation is suppressed via a Bose enhanced Quantum Zeno effect.
This is complementary to the quantum zeno control of phase-diffusion in a
bimodal condensate by symmetric noise (Phys. Rev. Lett. {\bf 100}, 220403
(2008)) in that the controlled process here is phase-{\it formation} and the
required decoherence mechanism for its suppression is purely phase noise.
