Highly portable, handheld instrument which can be pointed at the produce to be checked. Light from a source within the instrument is directed onto the produce to induce fluorescent emission from the produce, and fluorescent emissions from the produce are monitored with a detector within the instrument to detect the presence of pesticide residue on the produce. The light from the source is filtered to selectively pass light of a wavelength which induces maximum fluorescent emission from the pesticide to be detected, and the emissions from the produce are filtered to selectively pass emissions having a spectral content characteristic of the pesticide to be detected.