The study of the $\pi N\rightarrow \rho^0 N$ and
$\pi N \rightarrow \omega N$ amplitudes below and close to the
vector meson production threshold ($1.4<\sqrt s <1.8$ GeV)
reveals a rich structure arising from the presence of
baryon resonances in this energy range. These resonances are reflected in the
interference pattern of the $e^+e^-$ decays
of the $\rho^0$- and $\omega$-mesons produced in
$\pi^- p$ and $\pi^+ n$ reactions. We discuss
the shape and magnitude of the $\rho^0$-$\omega$ interference
in the $\pi^-p \rightarrow e^+e^- n$ and $\pi^+n \rightarrow e^+e^- p$
reaction cross sections
as functions of the total center of mass energy $\sqrt s$. We find contrasted results:
the interference is largely destructive for
the $\pi^-p \rightarrow e^+e^- n$ cross section but
constructive for the $\pi^+n \rightarrow e^+e^- p$ cross section.
An experimental study of these reactions would provide significant constraints
on the coupling of vector meson-nucleon channels to low-lying baryon resonances. | 
