I've looked some in the literature and come across the spectral response of crops under various pest pressure, but nothing specifically on the spectral signature of specific pests. Anyone have any articles or thoughts?
Dr. Claudio Gratton (entomology) and Dr. Phil Townsend (forest remote sensing) are working (...in part) on using spectroscopy to assess aphid-related disturbance effects on soybeans in Wisconsin. You could get in touch with them.