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DISTRIBUTION OF CONTARINIA OREGONENSIS FOOTE (DIPTERA: CECIDOMYIIDAE) EGGS IN DOUGLAS-FIR SEED ORCHARDS AND A METHOD OF ESTIMATING EGG DENSITY

  • G.E. Miller (a1)

Abstract

Efficient sampling procedures for estimating densities of eggs of Douglas-fir cone gall midge (DFCGM), Contarinia oregonensis Foote, on individual trees as well as for orchards were developed from data collected in Douglas-fir seed orchards in 1978–1981. Egg distribution was contagious and generally fitted the negative binomial distribution on individual trees, but a common k could not be estimated. Tree and crown level affected density of midge eggs within orchards. Average density at the midpoint of the cone-bearing portion of the crown was not significantly different from the tree average. The optimum sampling pattern in an orchard, i.e. one conelet from the midpoint of the cone-bearing portion of each of 120 trees, would require 120 person-hours to process the samples when DFCGM egg densities are high (worst-case situation).

À partir de données recueillies dans des vergers à graines de Douglas taxifolié de 1978 à 1981, on a élaboré des méthodes efficaces d’échantillonnage pour l’estimation de la densité des oeufs de Contarinia oregonensis Foote sur les arbres ainsi que dans les vergers. La distribution des oeufs était contagieuse et correspondait généralement à une distribution binomiale négative sur les arbres individuels, mais on n’a pas réussi à estimer un k commun. Le niveau dans l’arbre et dans la cime influait sur la densité des oeufs. La densité moyenne pour le milieu de la partie de la cime portant des cônes ne différait pas de façon significative de la densité moyenne pour l’arbre. Le plan optimal d’échantillonnage dans un verger, c’est-à-dire un cônelet par arbre dans 120 arbres, exigerait 120 heures-personnes pour le traitement des échantillons lorsque la densité des oeufs est élevée (pire cas).

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DISTRIBUTION OF CONTARINIA OREGONENSIS FOOTE (DIPTERA: CECIDOMYIIDAE) EGGS IN DOUGLAS-FIR SEED ORCHARDS AND A METHOD OF ESTIMATING EGG DENSITY

  • G.E. Miller (a1)

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