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DAMAGE PREDICTION FOR CONTARINIA OREGONENSIS FOOTE (DIPTERA: CECIDOMYIIDAE) IN DOUGLAS-FIR SEED ORCHARDS

Published online by Cambridge University Press:  31 May 2012

G.E. Miller
Affiliation:
Canadian Forestry Services, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5

Abstract

Damage at cone harvest by the Douglas-fir cone gall midge, Contarinia oregonensis Foote, was positively correlated with the number of egg-infested scales per conelet in the spring. Reducing the average number of galled seeds per cone by 1.5 increased the average number of filled seeds per cone by 1.0 in insecticide trials. Optimum sample sizes for estimating average densities of egg-infested scales were calculated to be one conelet per tree and 150 trees per orchard. The mean crowding variable was linearly related to average density so a sequential sampling technique relative to a critical density, using Iwao’s procedure, was developed for determining the need of control actions.

Résumé

Une corrélation positive a été établie entre les dommages causés à la récolte de cônes par la cécidomyie des cônes du Douglas (Contarinia oregonensis Foote) et le nombre d’écailles infestées par cônelet au printemps. La réduction de 1,5 obtenue lors d’essais de répression avec des insecticides du nombre moyen des graines touchées par cône a entraîné une augmentation du nombre moyen de graines pleines par cône de 1,0. Les tailles optimales des échantillons pour l’estimation de la densité moyenne des écailles infestées d’oeufs ont été calculées comme étant d’un cônelet par arbre et de 150 arbres par verger. Un rapport linéaire existant entre la variable d’encombrement moyen et la densité moyenne, une technique d’échantillonnage progressif en fonction de la densité critique, selon la méthode d’Iwao, a été élaborée pour déterminer la nécessité de mesures de répression.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1986

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