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ESTIMATING EPIDEMIC POPULATIONS OF THE LESSER MAPLE SPANWORM (LEPIDOPTERA: GEOMETRIDAE)1

Published online by Cambridge University Press:  31 May 2012

W. J. A. Volney
W. J. A. Volney
Affiliation:
Maritimes Forest Research Centre, Canadian Forestry Service, Fredericton, New Brunswick E3B 5P7
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Abstract

The distribution of lesser maple spanworm, Itame pustularia (Gn.) (Lepidoptera: Geometridae) larvae in red maple, Acer rubrum L., crowns and of pupae under these trees, and the relationship between the number of shoots on these trees and several easily-measured tree dimensions are used to design sampling techniques for estimating the mean number of larvae per shoot and the mean number of pupae per unit area in epidemic populations. An estimate of the total number of larvae per unit area is obtained from the product of larval density and the number of shoots per unit area. Some indication of how this latter estimate might be obtained is discussed. Because of the strong relationship between stem diameter and the number of shoots on a tree, a double sample procedure can be designed based on shoot counts from a relatively small number of trees. Auxiliary measurements on a large number of trees can improve the precision of the estimate.

Résumé

L’auteur utilise la distribution des larves de la Petite arpenteuse de l’Érable, Itame pustularia (Gn.) (Lépidoptères : Geometridés) dans les cimes de l’Érable rouge Acer rubrum L. et le nombre de pupes se trouvant sous ces arbres, puis le rapport entre le nombre de pousses trouvées sur ces arbres et plusieurs dimensions facilement mesurables, pour mettre au point un (design) des techniques d’échantillonnage visant à évaluer le nombre moyen de larves par pousse et aussi le nombre moyen de pupes par unité de surface dans les populations epidémeques. On obtient une estimation du nombre total de larves par unité de surface par le produit de la densité larvaire et du nombre de pousses par unité de surface. L’auteur disserte sur la manière de s’y prendre pour obtenir cette dernière estimation A cause du rapport important entre le diamètre de la tige et le nombre de pousses par arbre, on peut concevoir un processus de doublè échantillonnage fondé sur le nombre de pousses sur une quantité d’arbres relativement restreinte. Des mesurages additionnels sur un grand nombre d’arbres pourront améliorer la précision de l’évaluation.

Type
Articles
Information
The Canadian Entomologist , Volume 111 , Issue 2 , February 1979 , pp. 189 - 200
Copyright
Copyright © Entomological Society of Canada 1979

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