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Models for the Spread of Plant Disease: Some Experimental Results. K. P. Minogue, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; W. E. Fry, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 73:1173-1176. Accepted for publication 21 March 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1173.

Some predictions of two models of disease spread were examined in field experiments with potato late blight. The logit transformation was used to linearize disease gradients, and the gradient parameter (defined as the rate at which the logit of disease severity declines with distance) was constant after an initial stabilization period. Both rate-limiting resistance and fungicide treatment caused gradients to become significantly flatter. These results are consistent with model predictions. Contrary to predictions, the measured velocity of spread was unaffected by any treatment; some possible reasons for this result are discussed.