In vivo foliar spectroscopy offers the capacity to rapidly and non-destructively characterize plant physiological status which can be used to detect the effects of necrotizing pathogens on plant condition prior to visual symptoms. Dead tissue yields relatively consistent changes in leaf optical properties that challenges the ability to identify causal pathogen identity. Contact hyperspectral reflectance systems have been established as effective tools for rapid, early, real-time disease detection in crops, and for detecting physiological differences that enable pathogen discrimination. Here, we test the capacity of aerial, hyperspectral imaging spectroscopy to detect physiological effects of Phytophthora infestans (causal agent of late blight) over the course of disease development in the field. We previously have shown that hyperspectral reflectance can be used to identify both P. infestans and Alternaria solani (early blight) infected plants with 90% accuracy 2-4 days before symptoms appear. We measured continuous VSWIR reflectance (400-2500 nm) on four potato genotypes with two fungicide treatments in East Lansing, MI over the period of one month with a HYSPEX imaging spectrometer. We found this method could detect pathogen incidence and severity as low as 5-10%, and that deteriorating plant health could be detected within a week of inoculation. SWIR wavelengths (>1300 nm) were important for this detection. This offers great potential for use in early disease detection in field agricultural systems with the suite of hyperspectral satellites planned for the next decade.