  The IceCube neutrino spectrum shows a flux which falls of as $E^{-2}$ for sub
PeV energies but there are no neutrino events observed above $\sim 3$ PeV. In
particular the Glashow resonance expected at 6.3 PeV is not seen. We examine a
Planck scale Lorentz violation as a mechanism for explaining the cutoff of
observed neutrino energies around a few PeV. By choosing the one free parameter
the cutoff in neutrino energy can be chosen to be between 2 and 6.3 PeV. We
assume that neutrinos (antineutrinos) have a dispersion relation $E^2=p^2 -
(\xi_3/M_{Pl})~p^3$, and find that both $\pi^+$ and $\pi^-$ decays are
suppressed at neutrino energies of order of few PeV. We find that the $\mu^-$
decay being a two-neutrino process is enhanced, whereas $\mu^+$ decay is
suppressed. The $K^+\rightarrow \pi^0 e^+ \nu_e$ is also suppressed with a
cutoff neutrino energy of same order of magnitude, whereas $K^-\rightarrow
\pi^0 e^- \bar \nu_e$ is enhanced. The $n \rightarrow p^+ e^- \bar \nu_e$ decay
is suppressed (while the $\bar n \rightarrow p^- e^+ \nu_e$ is enhanced). This
means that the $\bar \nu_e$ expected from $n$ decay arising from $p+\gamma
\rightarrow \Delta \rightarrow \pi^+ n$ reaction will not be seen. This can
explain the lack of Glashow resonance events at IceCube. If no Glashow
resonance events are seen in the future then the Lorentz violation can be a
viable explanation for the IceCube observations at PeV energies.
