  The $\pi^-p \to e^+e^- n$ and $\pi^+n \to e^+e^- p$ reaction cross sections
are calculated below and in the vicinity of the vector meson ($\rho^0$,
$\omega$) production threshold. These processes are largely responsible for the
emission of $e^+e^-$ pairs in pion-nucleus reactions and contribute to the
dilepton spectra observed in relativistic heavy ion collisions. They are
dominated by the decay of low-lying baryon resonances into vector meson-nucleon
channels. The vector mesons materialize subsequently into $e^+e^-$ pairs. Using
$\pi N\to \rho^0 N$ and $\pi N \to \omega N$ amplitudes calculated in the
center of mass energy interval $1.4<\sqrt s <1.8$ GeV, we compute the $\pi^-p
\to e^+e^- n$ and $\pi^+n \to e^+e^- p$ reaction cross sections in these
kinematics. Below the vector meson production threshold, the $\rho^0 - \omega$
interference in the $e^+e^-$ channel appears largely destructive for the
$\pi^-p \to e^+e^- n$ cross section and constructive for the $\pi^+n \to e^+e^-
p$ cross section. The pion beam and the HADES detector at GSI offer a unique
possibility to measure these effects. Such data would provide strong
constraints on the coupling of vector meson-nucleon channels to low-lying
baryon resonances.
