A scanning spectroradiometer was used to measure the optical densities of an aerial photograph of an experimental field in which soybeans were growing in response to different concentrations of ozone, an air pollutant. The plants were growing in 3 m diameter, 2.4 m high open-top exposure chambers. Correlation coefficients among the film densities, plant yield and visual estimates of non-green leaf area for the 16 test plots were highly significant (p<0.0); those with ozone treatment concentrations were significant (p<0.05). The early senescence induced by this form of environmental stress can thus be detected by film density differences, and these differences are well correlated with ground indicators of crop condition. (Copyright (c) 1989 Taylor & Francis Ltd.)