The nonlinear evolution of the monochromatic whistler cyclotron resonance is responsible for a wide variety of geomagnetospheric phenomena whose interpretation has not taken into account the concomitant existence of whistler turbulence. Consideration of this whistler noise in the evolution of the coherent cyclotron resonance permits placing upper temporal bounds on the validity of the noiseless description of the interaction, and obtaining estimates for the relative intensity of the coherent mode and turbulent fields required for the onset of a typical nonlinear effect to occur. Particularization to the Siple wave injection experiment suggests that the influence of turbulence might be significant for monochromatic whistlers with weak or medium amplitudes (<100 m&ggr;).