Estimation of larval density of Liriomyza sativae Blanchard (Diptera: Agromyzidae) in cucumber greenhouses using fixed precision sequential sampling plans
This study was conducted to develop sequential sampling plans to estimate larval density of Liriomyza sativae Blanchard (Diptera: Agromyzidae) at three precision levels in cucumber greenhouse. The within- greenhouse spatial patterns of larvae were aggregated. The slopes and intercepts of both Iwao’s patchiness regression and Taylor’s power law did not differ between years. A fixed-precision level sampling plan was developed using the parameters of Taylor’s power law generated from total number of larvae in a cucumber leaf at three precision levels (D) of 0.1, 0.25 and 0.28. The resulting sampling plans were tested with sequential bootstrap simulations (n = 500) using 10 independent data sets for validation. Bootstrap simulation within a wide range of densities demonstrated that actual D' values at desired D= 0.28 averaged < 0.28 in all cases. Even at the lowest density of larvae (0.24 larvae per leaf), the actual mean D' was 0.25 at D= 0.28. This result shows that the sampling plan developed in this study is effective and reliable for estimating the larval densities in cucumber greenhouses.
Key words: Vegetable leafminer, sequential sampling, spatial distribution, greenhouse cucumber.