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Late Blight Detection in Tomato Fields by Aerial Photography with Natural and Infrared Color Film. C. H. Blazquez, University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, Lake Alfred 33850. . Plant Dis. 74:589-592. Accepted for publication 22 January 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0589.

Natural color and infrared color aerial photographs of tomato (Lycopersicon esculentum) canopies were taken weekly with paired 35-mm cameras during the 1976 spring growing season. Loci of tomato late blight infections (caused by Phytophthora infestans) confirmed by field surveillance were drawn on field maps and compared with results of photographic analysis. Spectral densitometric measurements made on films from 400 to 700 nm in increments of 10 nm showed two intensity peaks with both types of film. Dividing the first peak by the second peak produced a ratio greater than 1 that correlated significantly with integral and transmittance measurements of color infrared photographs of diseased plants. Spectrophotometric measurements of color infrared photographs detected late blight on tomato plants better than visual observation of photographs.