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SAMPLING OVERWINTERING JACK PINE BUDWORM, CHORISTONEURA PINUS PINUS FREE. (LEPIDOPTERA: TORTRICIDAE), AND TWO OF ITS PARASITOIDS (HYMENOPTERA)

Published online by Cambridge University Press:  31 May 2012

V.G. Nealis  and
T.J. Lysyk
V.G. Nealis
Affiliation:
Canadian Forestry Service, Great Lakes Forestry Centre, PO Box 490, Sault Ste. Marie, Ontario, Canada, P6A 5M7
T.J. Lysyk
Affiliation:
Canadian Forestry Service, Great Lakes Forestry Centre, PO Box 490, Sault Ste. Marie, Ontario, Canada, P6A 5M7
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Abstract

Data on the distribution of overwintering jack pine budworm (Choristoneura pinus pinus Free.) collected between 1985 and 1987 in northern Ontario are used to develop guidelines for sampling this stage of the budworm. Two alternative methods of expressing budworm density are considered: counting the number of budworms per metre of branch and counting the number per square metre of branch bark surface area. Estimates of budworm density for three levels in the tree’s crown are given for 4 site-years.

Entire branches are recommended as the sample units as the use of 60-cm branch-tip sections resulted in consistent underestimation of actual density per branch. Jack pine budworm density did not vary among cardinal compass directions and was generally highest at mid-crown levels.

The distributions of two parasitoids, Apanteles fumiferanae Vier. and Glypta fumiferanae (Vier.), which overwinter as an egg or first-instar larva within the jack pine budworm, also were considered. Apanteles was the most abundant parasitoid at all crown levels at all sites examined. Percentage parasitism by Apanteles was highest and that by Glypta was lowest on the branch-tip sections in relation to the branch-basal section, but total percentage parasitism was relatively constant over the entire branch, throughout the tree crown, and from tree to tree. Consequently, the sampling method for jack pine budworm is easily extended for estimating the rate of parasitism and therefore for providing a prediction of mortality that results from these two common parasitoids.

Résumé

Les données concernant la distribution de la tordeuse du pin gris (Choristoneura pinus pinus Free.) qui hiberne, recueillies entre 1985 et 1987 dans le nord de l’Ontario, servent à préparer des directives d’échantillonnage de cette tordeuse rendue à ce stade. Deux méthodes possibles d’exprimer la densité des tordeuses sont considérées : le dénombrement des tordeuses par mètre de branche et le dénombrement par mètre carré de superficie des branches. L’évaluation de la densité des tordeuses est donnée en fonction de trois niveaux dans la cime des arbres et pour 4 stations-années.

Il est recommandé d’utiliser des branches entières comme échantillons puisque le recours à des sections distales de 60 cm des branches conduit régulièrement à une sous-estimation de la densité réelle par branche. La densité des tordeuses du pin gris ne variait pas selon l’orientation géographique et elle était généralement la plus élevée à mi-hauteur de la cime.

Les distributions de deux parasitoïdes, Apanteles fumiferanae Vier. et Glypta fiimiferanae (Vier.), qui hibernent au stade d’œuf ou de premier instar dans la tordeuse du pin gris, ont également été étudiées. Apanteles était le parasitoïde le plus abondant dans tous les niveaux de la cime et à toutes les stations considérées. En pourcentage, le parasitisme par Apanteles était le plus élevé et celui par Glypta était le plus faible dans les sections distales des branches par rapport à la section proximale, mais le parasitisme total en pourcentage était relativement constant pour la branche considérée dans son entier, partout dans la cime et d’un arbre à l’autre. Par conséquent, la méthode d’échantillonnage des tordeuses du pin gris se prête facilement à l’évaluation du taux de parasitisme et donc permet d’obtenir une prévision de la mortalité attribuable à ces deux parasitoïdes communs.

Type
Articles
Information
The Canadian Entomologist , Volume 120 , Issue 12 , December 1988 , pp. 1101 - 1111
Copyright
Copyright © Entomological Society of Canada 1988

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