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A Study of Distribution and Sampling of Soybean Plants Naturally Infected with Pseudomonas syringae pv. glycinea. G. Poushinsky, Statistician, at the Engineering and Statistical Research Institute and Ottawa Research Station, Agriculture Canada, Ottawa, Ontario, K1A 0C6; P. K. Basu, plant pathologist, at the Engineering and Statistical Research Institute and Ottawa Research Station, Agriculture Canada, Ottawa, Ontario, K1A 0C6. Phytopathology 74:319-326. Accepted for publication 30 August 1983. 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, 1984. DOI: 10.1094/Phyto-74-319.

Soybean (Glycine max) plants were grown in a field plot (42.7 by 53.9 m) at Ottawa in 1978, and similar sized areas from eight farmers' fields were examined in 1982 for the presence of bacterial blight caused by Pseudomonas syringae pv. glycinea. Tagged plants were assessed several times during the growing season. The pattern of disease occurrence was investigated by using three existing indices of nonrandomness and a fourth method was proposed and applied. Diseased plants were distributed nonrandomly from early to midseason. Samples of various sizes following three types of sampling paths were taken to estimate disease incidence. Simple random samples were inadequate to assess disease percentage when the underlying disease distribution was nonrandom.