Surface plasmon polariton scattering from 2D subwavelength silicon wires is investigated using the finitedifference time-domain method. It is shown that coupling an incident surface plasmon polariton to intercavity modes of the particle can dramatically change transmitted fields and plasmon-induced forces. In particular, both transmission and optical forces are highly sensitive to the particle size that is related to the excitation of whispering gallery modes or standing wave modes depending on the particle shape and size. These features might have potential sensing applications.