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A NEW PROCEDURE FOR RAPIDLY ESTIMATING EUROPEAN PINE SAWFLY (HYMENOPTERA: DIPRIONIDAE) POPULATION LEVELS IN YOUNG PINE PLANTATIONS1

Published online by Cambridge University Press:  31 May 2012

Louis F. Wilson  and
Douglas J. Gerrard
Louis F. Wilson
Affiliation:
North Central Forest Experiment Station, Forest Service, U.S. Department of Agriculture
Douglas J. Gerrard
Affiliation:
Department of Forestry, University of Minnesota, St. Paul
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Abstract

A method is proposed for rapidly estimating the population levels of European pine sawfly in young red and Scotch pine plantations. On the hypothesis that the numbers of larval colonies per tree are distributed within a stand according to a negative binomial series, it is shown that an estimate Y of the mean sawfly count per tree in any relevant pine stand may be predicted from knowledge of the proportion p of trees infested, by means of the equation

in which k is an estimate of a distribution parameter. The estimate k is derived beforehand, by Maximum Likelihood from a series of insect populations representative of those in which predictions are contemplated.Approximate 95% confidence limits for estimated densities are computed from a variance estimator reflecting two sources of error. The plotted confidence bands pertaining to samples of various size furnish a simple criterion for judging directly from the proportion of infested trees whether or not suppression measures are needed in a plantation.

Type
Articles
Information
The Canadian Entomologist , Volume 103 , Issue 9 , September 1971 , pp. 1315 - 1322
Copyright
Copyright © Entomological Society of Canada 1971

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