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DISTRIBUTION OF OVERWINTERING BIRCH CASEBEARER LARVAE, COLEOPHORA FUSCEDINELLA, ON WHITE BIRCH (LEPIDOPTERA: COLEOPHORIDAE)

Published online by Cambridge University Press:  31 May 2012

A. G. Raske  and
D. G. Bryant
A. G. Raske
Affiliation:
Newfoundland Forest Research Centre, Canadian Forestry Service, St. John's
D. G. Bryant
Affiliation:
Newfoundland Forest Research Centre, Canadian Forestry Service, St. John's
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Abstract

The majority (about 94%) of birch casebearer larvae, Coleophora fuscedinella Zeller, abandon the leaves in the fall and attach their case to the bark surface at spurs, at the base of buds, and at twig crotches. Casebearer populations were studied in six white birch, Betula papyrifera Marsh., stands of 3 m to 6 m in height. An average of 50% of overwintering population of the birch casebearer occurred within 50 cm of the crown periphery of the middle half of the crown. This proportion was the same at the three population densities studied: 2,000, 10,000, and 20,000 cases per tree. Intra-tree distribution differed significantly between stands and between years and was modified when there were more than 3,000 larvae in a tree. However, the relation between log10 (cases + 1) at midcrown and the whole tree was consistent and usually explained more than 85% of the variance. For all population densities, the number of casebearers in the tree could be estimated from a sample of the crown. To preserve the form and aesthetic value of trees, the sample should comprise spurs or crotches and not a crown sector as used in this study.

Résumé

En automne les larves du porte-case du bouleau, Coleophora fuscedinella Zeller, dans leurs cases abandonnent les feuilles et la majorité (à peu près 94%) s’attache à l’écorce à la base des brindilles ou lambourde et au fourchets des rameaux. Les populations de l’insecte ont été étudiées dans six peuplements de bouleau blanc, Betula papyrifera Marsh, de 3 m à 6 m de hauteur. Dans trois groupes de population, c’est à dire 2,000, 10,000 et 20,000 cases à l’arbre dans un peuplement, au moyenne 50% des cases se trouve dans les 50 cm apicale au milieu d’une couronne d’arbre. La distribution des cases est modifiée par le nombre des bourgeons, quand il y a plus de 3,000 larve dans un arbre. D’autre part, la corrélation entre la nombre logarithme10 (des cases + 1) dans le milieu de la couronne et celle dans l’arbe entière a été constant et a expliqué plus que 85% de la variation. Pour toutes groupes de population, on peut estimer le nombre des cases dans un arbre par un échantillon de la couronne. Pour conserver la forme et la valeur esthétique, on doit prendre un échantillon des brindilles ou des fourchets, pas un secteur que nous nous sommes servis.

Type
Articles
Information
The Canadian Entomologist , Volume 108 , Issue 4 , April 1976 , pp. 407 - 414
Copyright
Copyright © Entomological Society of Canada 1976

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