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Ecology and Epidemiology

Evaluation of Tests for Randomness of Infected Plants. L. V. Madden, Systems specialist, Department of Plant Pathology, Ohio Agricultural Research and Development Center, U.S. Department of Agriculture, Wooster, OH 44691; Raymond Louie(2), J. J. Abt(3), and J. K. Knoke(4). (2)(3)(4)Research plant pathologist, agricultural research technician, and research entomologist, respectively, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, Wooster, OH 44691. Phytopathology 72:195-198. Accepted for publication 31 March 1981. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982. DOI: 10.1094/Phyto-72-195.

A study was conducted to evaluate ordinary runs, original doublets, and corrected doublets for detecting the pattern of sweet corn plants infected by maize dwarf mosaic virus. Four fields were divided into a total of 636 quadrats and analyzed with each test. When the data were divided into 10% ranges of infected plants, no trend in the agreement between ordinary runs and original doublets or between ordinary runs and corrected doublets was evident. For original and corrected doublets, agreement ranged from 100% at the lowest disease incidence to 0% at the highest level of incidence. In a simulation study, corrected doublets gave unsatisfactory results (>5% misclassifications) when random patterns were generated, original doublets gave unsatisfactory results when nonrandom patterns were generated, whereas ordinary runs did not give unsatisfactory results with random or nonrandom patterns. Thus, ordinary runs was the best test for determining randomness of infected plants.