Abstract
Cyst nematodes are serious plant-parasitic pests which could cause severe yield losses and extensive damage. Since there is still very little information about error of population density estimation in small field plots, this study contributes to the broad issue of population density assessment. It was shown that there was no significant difference between cyst counts of five or seven bulk samples taken per each 1-m2 plot, if average cyst count per examined plot exceeds 75 cysts per 100 g of soil. Goodness of fit of data to probability distribution tested with χ2 test confirmed a negative binomial distribution of cyst counts for 21 out of 23 plots. The recommended measure of sampling precision of 17% expressed through coefficient of variation (cv) was achieved if the plots of 1 m2 contaminated with more than 90 cysts per 100 g of soil were sampled with 10-core bulk samples taken in five repetitions. If plots were contaminated with less than 75 cysts per 100 g of soil, 10-core bulk samples taken in seven repetitions gave cv higher than 23%. This study indicates that more attention should be paid on estimation of sampling error in experimental field plots to ensure more reliable estimation of population density of cyst nematodes.
Highlights
Cyst nematodes are serious plant-parasitic pests which could cause severe yield losses and extensive damage
The zigzag pattern was a modification of the rectangular grid which increases the probability of including individuals form every area within the plot to the population density estimation and facilitates sampling of two rows in one passage over the sampling area
Variation of cyst counts per plot: To investigate whether there was a difference between triplets analyzed per each 1-m2 plot, statistical tests on the means were employed
Summary
Cyst nematodes are serious plant-parasitic pests which could cause severe yield losses and extensive damage. There is still very little information about soil sampling error in field experiments conducted in small field plots These experiments are often related to resistance/tolerance testing and development of control measures which need higher precision for estimating population densities than are required for nematode management (Francl, 1986). The coefficient of variation, as a measure of sampling precision, is usually used to indicate sampling error of cyst counts over large area to make an advisory system more efficient; estimation of sampling error for cyst counts of small field plots is rarely provided (Seinhorst, 1986; Heijbroek et al, 2002).
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