Spatial distribution pattern and sequential sampling plans for Bactrocera oleae (Gmelin) (Dip: Tephritidae) in olive orchards

The distribution of adult and larvae Bactrocera oleae (Diptera: Tephritidae), a key pest of olive, was studied in olive orchards. The first objective was to analyze the dispersion of this insect on olive and the second was to develop sampling plans based on fixed levels of precision for estimating B. oleae populations. The Taylor’s power law and Iwao’s patchiness regression models were used to analyze the data. Our results document that Iwao’s patchiness provided a better description between variance and mean density. Taylor’s b and Iwao’s β were both significantly more than 1, indicating that adults and larvae had aggregated spatial distribution. This result was further supported by the calculated common k of 2.17 and 4.76 for adult and larvae, respectively. Iwao’s a for larvae was significantly less than 0, indicating that the basic distribution component of B. oleae is the individual insect. Optimal sample sizes for fixed precision levels of 0.10 and 0.25 were estimated with Iwao’s patchiness coefficients. The optimum sample size for adult and larvae fluctuated throughout the seasons and depended upon the fly density and desired level of precision. For adult, this generally ranged from 2 to 11 and 7 to 15 traps to achieve precision levels of 0.25 and 0.10, respectively. With respect to optimum sample size, the developed fixed-precision sequential sampling plans was suitable for estimating flies density at a precision level of D=0.25. Sampling plans, presented here, should be a tool for research on pest management decisions of B. oleae.

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Developing Optimum Sample Size and Multistage Sampling Plans for Lobesia botrana (Lepidoptera: Tortricidae) Larval Infestation and Injury in Northern Greece

Journal of Economic Entomology ◽

10.1603/0022-0493-99.5.1890 ◽

2006 ◽

Vol 99 (5) ◽

pp. 1890-1898 ◽

Cited By ~ 4

Author(s):

A. A. Ifoulis ◽

M. Savopoulou-soultani

Keyword(s):

Sample Size ◽

Lobesia Botrana ◽

Northern Greece ◽

Sampling Plans ◽

Optimum Sample Size ◽

Multistage Sampling ◽

Optimum Sample

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Optimum sample size to estimate mean parasite abundance in fish parasite surveys

Helminthologia ◽

10.1515/helm-2017-0054 ◽

2018 ◽

Vol 55 (1) ◽

pp. 52-59 ◽

Cited By ~ 7

Author(s):

S. Shvydka ◽

V. Sarabeev ◽

V. D. Estruch ◽

C. Cadarso-Suárez

Keyword(s):

Sample Size ◽

Sample Size Determination ◽

Superior Performance ◽

Size Determination ◽

Optimum Sample Size ◽

True Value ◽

Wide Range ◽

Precision Level ◽

The Mean ◽

Optimum Sample

Summary To reach ethically and scientifically valid mean abundance values in parasitological and epidemiological studies this paper considers analytic and simulation approaches for sample size determination. The sample size estimation was carried out by applying mathematical formula with predetermined precision level and parameter of the negative binomial distribution estimated from the empirical data. A simulation approach to optimum sample size determination aimed at the estimation of true value of the mean abundance and its confidence interval (CI) was based on the Bag of Little Bootstraps (BLB). The abundance of two species of monogenean parasites Ligophorus cephali and L. mediterraneus from Mugil cephalus across the Azov-Black Seas localities were subjected to the analysis. The dispersion pattern of both helminth species could be characterized as a highly aggregated distribution with the variance being substantially larger than the mean abundance. The holistic approach applied here offers a wide range of appropriate methods in searching for the optimum sample size and the understanding about the expected precision level of the mean. Given the superior performance of the BLB relative to formulae with its few assumptions, the bootstrap procedure is the preferred method. Two important assessments were performed in the present study: i) based on CIs width a reasonable precision level for the mean abundance in parasitological surveys of Ligophorus spp. could be chosen between 0.8 and 0.5 with 1.6 and 1x mean of the CIs width, and ii) the sample size equal 80 or more host individuals allows accurate and precise estimation of mean abundance. Meanwhile for the host sample size in range between 25 and 40 individuals, the median estimates showed minimal bias but the sampling distribution skewed to the low values; a sample size of 10 host individuals yielded to unreliable estimates.

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