  We present the effective lagrangian for low energy and momentum spin waves in
canted phases at next to leading order in the derivative expansion. The
symmetry breaking pattern SU(2) --> 1 of the internal spin group and that of
the crystallographic space group imply that there is one ferromagnetic and one
antiferromagnetic spin wave. The interaction of the spin waves with the charge
carriers is also discussed for canted, ferromagnetic and antiferromagnetic
phases. All this together allows us to write the doping dependence of the
dispersion relation parameters for doped manganites. We point out that the spin
waves posses distinctive characteristics which may allow us to experimentally
differentiate canted phases from phase separation regions in doped manganites.
