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DISTRIBUTION OF EGGS OF WESTERN BLACKHEADED BUDWORM, ACLERIS GLOVERANA (WALSINGHAM) (LEPIDOPTERA: TORTRICIDAE), AND OF FOLIAGE OVER THE CROWNS OF 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:
Forestry Canada, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
T.G. Gray
Affiliation:
Forestry Canada, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
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Abstract

Eggs of western blackheaded budworm, Acleris gloverana (Walsingham), were found on the underside of needles of western hemlock, Tsuga heterophylla (Raf.) Sarg., with higher densities in the mid-crown area toward the outer tips of branches. Fringe and dominant trees were preferred oviposition sites over trees in lower crown classes or shaded positions. Vertical differences in needle density were considerable and led to high variability in insect densities when expressed on a per branch basis. When densities of eggs were based on a fresh branch weight basis there was a significant decrease in sample bias caused by the uneven distribution of foliage over the crowns.

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. Leur densité est supérieure à mi-cime vers la partie terminale des branches. Les arbres dominants et ceux situés en bordure de forêt sont préférés pour l’oviposition comparativement aux arbres de classes de hauteurs inférieures ou situés à l’ombre. La densité des aiguilles varie considérablement selon la verticale et ceci induit une grande variabilité des densités d’insectes lorsqu’elles sont exprimées par unité de branche. Lorsque les densités des oeufs sont présentées en fonction du poids frais des branches, il y a une diminution significative du biais d’échantillonnage causée par une distribution inégale du feuillage dans la cime.

Type
Articles
Information
The Canadian Entomologist , Volume 122 , Issue 3 , June 1990 , pp. 547 - 554
Copyright
Copyright © Entomological Society of Canada 1990

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