Spatial Distribution and Precision of Sampling of Pratylenchus Zeae Populations in a Maize Field

The spatial distribution of Pratylenchus zeae in a maize field conformed to the negative binomial model. The parameters of this model were compared with those of Taylor's Power Law in two consecutive years and related to the area of sampled plot. The ‘k’ value of the negative binomial model was negatively correlated with the logarithms of plot area while the ‘b’ value of Taylor's Power Law was positively correlated. The number of cores necessary for estimating the population density with 10 or 25 per cent precision was determined and regressed on plot area. Due to variations of the parameters in the two years the number of cores necessary for the same degree of precision varied. The desired number of cores for 25 per cent precision and 95 per cent confidence varied from 75 to 124 in 1986 and from 47 to 68 in 1987 with increase in plot area from 100 to 1000 m². Some suggestions have been made to enable reduction in the number of cores such as by improving/automation of extraction techniques.