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A SAMPLING SYSTEM FOR EGGS OF WESTERN BLACKHEADED BUDWORM, ACLERIS GLOVERANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE), ON WESTERN HEMLOCK, TSUGA HETEROPHYLLA (RAF.) SARG.

Published online by Cambridge University Press:  31 May 2012

R.F. Shepherd  and
T.G. Gray
R.F. Shepherd
Affiliation:
Pacific Forestry Centre, Forestry Canada, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
T.G. Gray
Affiliation:
Pacific Forestry Centre, Forestry Canada, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
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Abstract

Eggs of western blackheaded budworm, Acleris gloverana (Walsingham), are laid on the lower surface of western hemlock, Tsuga heterophylla (Raf.) Sarg., needles. A comparison was made of the following measures of sample branch size as a basis for expressing egg density: fresh branch weight, branch area, total twig length, branch volume, and number of buds. The criteria for selection of these measures were as follows: correlations of branch size with dry needle weight, variances of egg density and their relative contribution to sample size, and ease of measurement. Fresh branch weight was the best choice. A sequential sampling system was developed on this basis and was related to a scale of predicted defoliation. In addition, a transformation was provided for use in data analysis.

Résumé

Les oeufs de la tordeuse à tête noire de l’ouest, Acleris gloverana (Walsingham), sont placés sur la surface inférieure des aiguilles de la pruche de l’ouest, Tsuga heterophylla (Raf.) Sarg. On a comparé certaines mesures relatives à la taille des branches échantillons afin de représenter la densité des oeufs : poids frais de la branche, surface de la branche, longueur totale des pousses, volume de la branche et nombre de bourgeons. Les critères de sélection de ces mesures ont été : la corrélation entre la taille de la branche avec le poids sec des aiguilles, la variabilité de la densité des oeufs ainsi que leur contribution relative à la taille de l’échantillon et finalement la facilité de la prise de la mesure. Le meilleur critère a été le poids frais de la branche. Une méthode d’échantillonnage séquentiel a été développée en tenant compte de ce critère et a été reliée à une échelle de prédiction de la défoliaison. De plus, une transformation est indiquée afin d’être utilisée dans l’analyse des données.

Type
Articles
Information
The Canadian Entomologist , Volume 122 , Issue 3 , June 1990 , pp. 555 - 562
Copyright
Copyright © Entomological Society of Canada 1990

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