rapidly collect important information Delp, B. R., Stowell, L. J., and Marois, J. J. 1986. Field runner: A disease incidence, severity, and about plant disease incidence, sevi spatial pattern assessment system. Plant Disease 70:954-957. and spatial pattern with a system that is efficient and achieves levels of accuracy A computer software system titled Field Runner was developed to facilitate the assessment of plant not practically possible with conventional disease incidence, severity, and spatial pattern in fields. Field Runner used the stratified random sampling systems. sampling design to provide an unbiased sample and a lower percent error of the disease incidence Sampling strategy. Previously used estimates than previously used sampling designs (diagonal, X, or W). The computer directed sampling techniques included W, the operator to each sample site, stored the data, and provided an immediate analysis. Analyses and diagonal designs across a portion or included 1) the estimated mean and variance of disease incidence, 2) the variance-to-mean ratio, 3) all of the field (2,13) (Fig. 1 A-D). an estimate of the k parameter of the negative binomial distribution, 4) an estimate of Lloyd's Usually, plants were evaluated at ran indices of mean crowding and mean patchiness, and 5) the Z-score from an ordinary runs analysis. Usuallysplants were evaluatednat a Fields could be assessed for severity of one disease or for incidence of one to several diseases intervals along these paths. Lin et al (13) simultaneously. Lettuce and alfalfa fields were sampled to test the performance of Field Runner and Basu et al (2) compared the relative under actual conditions. The incidences and aggregation indices for anthracnose and drop of accuracies of these sampling designs and lettuce and severity of alfalfa plant damage caused by alkali soil are reported. Lettuce anthracnose determined that partial-field samples and alfalfa plant damage were aggregated in foci; lettuce drop occurred randomly in the field. provided the least accurate estimates of disease. There was little difference in the accuracies of the designs across the whole Knowledge of plant disease incidence MATERIALS AND METHODS field if the disease was randomly (number of infected plants or plant units Field Runner, the computer software distributed; however, X and W expressed as a percentage of the total system described in this paper, simplifies designs were more accurate than the number assessed [12]), severity, and the task of sampling fields. The system is diagonal design if disease was aggregated. spatial pattern is becoming increasingly designed to aid in the rapid and accurate Maximum dispersal of sample sites along important as the economics of agriculture assessment of disease incidence, severity, the sampling design was the most require more critical decisions at all and spatial pattern in the field. Field important factor to obtain accurate levels. Government, public, and private Runner uses the stratified random estimates of disease incidence if disease institutions use this information to sampling design (SRSD) with single- was aggregated (13). evaluate their long-term research goals stage cluster sampling (5), in which the In the SRSD, fields are divided into and resource allocations (4,12). Growers field is divided into equal-sized sectors sectors of equal size (stratification) and and agricultural advisors use it to make and a randomly located sample is plants are evaluated at a random location pest management decisions. It is an initial collected within each sector. Stratified within each sector (Fig. 1 E) (5). Thus, factor for an epidemiologist to study random sampling provides accurate sample sites are distributed thoroughout disease development. Disease incidence, estimates of disease incidence (8), but it the field without bias to any section of the severity, and spatial pattern depend on was too cumbersome in the past to be field. Preliminary results from application data obtained from field samples. The practical. The system, however, incorpo- of the SRSD to plant diseases have been accuracy of these data, as well as the time rates a field-portable microcomputer, reported (7). This sampling technique and effort required to obtain them, is and as a result, this sampling design can was tested and compared with the W affected by the sampling technique used. now be used more efficiently. The system and diagonal designs for accuracy of Therefore, a desirable sampling technique prompts the operator for necessary estimating the mean disease incidence for would provide the most accurate data for information about the field and disease(s) the entire field (8). The SRSD was more a minimum associated cost. to be sampled. It then directs the accurate than the W or diagonal operator to each sample site, stores the designs if sample intensity was greater data, and provides an immediate than 0.2%. In addition to increased analysis. As a result, agricultural accuracy of the estimate of the mean,
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Jan 1, 1995
Michael J Wade 
Open Access