  We use QCD light-cone sum rules (LCSR) with holographic anti de
Sitter/Chromodynamics (AdS/QCD) Distribution Amplitudes (DAs) for the $\rho$
meson to predict the form factors that govern the leading amplitudes of the
rare radiative $B -> \rho \gamma$ decay and the semileptonic decay $B -> \rho l
\nu$. We test the Isgur-Wise relation between the radiative and semileptonic
form factors. We also compute the total width (in units of $|V_{ub}|^2$) for
the semileptonic decay $B -> \rho l \nu$ as well as ratios of partial decay
widths which are independent of $|V_{ub}|$.
