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A SEQUENTIAL SAMPLING PLAN FOR ADULT TUBER FLEA BEETLES (EPITRIX TUBERIS GENTNER): DEALING WITH “EDGE EFFECTS”

Published online by Cambridge University Press:  31 May 2012

Michel Cusson ,
Robert S. Vernon  and
Bernard D. Roitberg
Michel Cusson
Affiliation:
Department of Biological Sciences, Centre for Pest Management, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
Robert S. Vernon
Affiliation:
Agriculture Canada, Vancouver Research Station, 6660 West Marine Drive, Vancouver, British Columbia, Canada V6T 1X2
Bernard D. Roitberg
Affiliation:
Department of Biological Sciences, Centre for Pest Management, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
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Abstract

We propose a sequential sampling plan for adult tuber flea beetles, Epitrix tuberis Gent., in potato fields, which is based on a confidence interval calculated around a critical density value (Iwao 1975) and which uses Taylor’s Power Law (Taylor 1961) to estimate the variance. Because of the highly edge-biased gradients of density displayed by this insect, separate sequential expressions have been calculated for densities at the edges and centers of fields.

In a survey of 12 commercial potato fields, spring-generation E. tuberis densities in centers of fields were always far below the threshold level of one beetle per 10 plants employed at the time of sampling. The survey also indicated that fields that have been sown with potatoes for 2 consecutive years have higher beetle densities than fields sown with potatoes for a 1st year. Edge:center density ratios, however, were the same for the two categories of fields.

Résumé

Nous proposons un programme d’échantillonnage séquentiel pour les adultes de l’altise du tubercule, Epitrix tuberis Gent., basé sur l’emploi d’un intervalle de confiance calculé autour d’une valeur critique de densité (Iwao 1975) et utilisant “Taylor's Power Law” (Taylor 1961) pour estimer la variance. En raison des densités d’altises généralement beaucoup plus élevées en bordure qu’au centre des champs, des expressions séquentielles différentes ont été calculées pour ces deux strates d’échantillonnage.

Dans le cadre d’une étude menée dans 12 champs commerciaux de pommes de terre, les densités d’altises de la génération hivernante, au centre des champs, étaient toujours de beaucoup inférieures à la valeur seuil d’une altise par 10 plants utilisée au moment de l’échantillonnage. De cette étude il est aussi ressorti que les champs dans lesquels les pommes de terre sont cultivées pour une 2ème année consécutive ont de plus fortes densités d’altises que ceux dans lesquels les pommes de terre sont cultivées pour une 1ère année. Cependant, les rapports de densité bordurexentre étaient les mêmes pour ces deux catégories de champs.

[Traduit par l’auteur]

Type
Articles
Information
The Canadian Entomologist , Volume 122 , Issue 3 , June 1990 , pp. 537 - 546
Copyright
Copyright © Entomological Society of Canada 1990

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