Cereal pests and diseases can significantly reduce potential crop yields. Correct and timely identification in-field is key to their control. This chapter summarizes and evaluates some of the many available methods for detection of pests and diseases, ranging from classical methods of plant pathology, such as visual or microscopic recognition, to new DNA sequencing technologies. We discuss how protein-based-diagnostics that rely on specificity of antibodies, such as variations on ELISA detection and dipstick or lateral flow devices, have been extended to protein profiling by MALDI-TOF mass spectrometry. However, nucleic-acid-based amplification techniques using various forms of polymerase chain reaction are now widely implemented, including isothermal amplification and in-field pathogen detection. The chapter shows how the molecular diagnostic techniques are being rapidly supplemented with image-based diagnostics, which rely on hyperspectral imaging, applied via satellites or drones for regional- or field-scale monitoring of disease incidence and progression.