The nonlinear coupling of a low-frequency electron quasi-mode and ahigh-frequency electrostatic wave through a high-frequency electromagneticpump is considered in a dusty plasma, which includes the effect of dustcharging. The electron quasi-mode occurs in a dusty plasma whose electronDebye length and electron temperature are much greater than, respectively,the ion Debye length and the ion temperature. The nonlinear dispersionrelation has a structure that is much simpler than the nonlinear dispersionrelation for the parametric instability in dust-free plasmas. Only a purelygrowing instability can be excited, and the threshold and growth rate areobtained.