  A well known theorem of Duflo claims that the annihilator of a Verma module
in the enveloping algebra of a complex semisimple Lie algebra is generated by
its intersection with the centre. For a Lie superalgebra this result fails to
be true. For instance, in the case of the orthosymplectic Lie superalgebra
osp(1,2), Pinczon gave in [Pi] an example of a Verma module whose annihilator
is not generated by its intersection with the centre of universal enveloping
algebra. More generally, Musson produced in [Mu1] a family of such "singular"
Verma modules for osp(1,2l) cases.
  In this article we give a necessary and sufficient condition on the highest
weight of a $\osp(1,2l)$-Verma module for its annihilator to be generated by
its intersection with the centre. This answers a question of Musson.
