  The odd symplectic Grassmannian $\mathrm{IG}:=\mathrm{IG}(k, 2n+1)$
parametrizes $k$ dimensional subspaces of $\mathbb{C}^{2n+1}$ which are
isotropic with respect to a general (necessarily degenerate) symplectic form.
The odd symplectic group acts on $\mathrm{IG}$ with two orbits, and
$\mathrm{IG}$ is itself a smooth Schubert variety in the submaximal isotropic
Grassmannian $\mathrm{IG}(k, 2n+2)$. We use the technique of curve
neighborhoods to prove a Chevalley formula in the equivariant quantum
cohomology of $\mathrm{IG}$, i.e. a formula to multiply a Schubert class by the
Schubert divisor class. This generalizes a formula of Pech in the case $k=2$,
and it gives an algorithm to calculate any multiplication in the equivariant
quantum cohomology ring.
