Field Runner: A Disease Incidence, Severity, and Spatial Pattern Assessment System

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Abstract
A computer software system titled Field Runner was developed to facilitate the assessment of plant disease incidence, severity, and spatial pattern in fields. Field Runner used the stratified random sampling design to provide an unbiased sample and a lower percent error of the disease incidence estimates than previously used sampling designs (diagonal, "X", or "W"). The computer directed the operator to each sample site, stored the data, and provided an immediate analysis. Analyses included 1) the estimated mean and variance of disease incidence, 2) the varianc-to-mean ratio, 3) an estimate of the k parameter of the negative binomial distribution, 4) an estimate of Lloyd''s indices of mean crowding and mean patchiness, and 5) the Z-score from an ordinary runs analysis. Fields could be assessed for severity of one disease or for incidence of one to several diseases simultaneously. Lettuce and alfalfa fields were sampled to test the performance of Field Runner under actual conditions. The incidences and aggregation indices for anthracnose and drop of lettuce and severity of alfalfa plant damage caused by alkali soil are reported. Lettuce anthracnose and alfalfa plant damage were aggregated in foci; lettuce drop occurred randomly in the field.

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