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Seasonal changes in seed reduction in lodgepole pine cones caused by feeding of Leptoglossus occidentalis (Hemiptera: Coreidae)

Published online by Cambridge University Press:  02 April 2012

Ward B. Strong
Ward B. Strong
Affiliation:
British Columbia Ministry of Forests and Range, Kalamalka Forestry Centre, 3401 Reservoir Road, Vernon, British Columbia, Canada V1B 2C7 (e-mail: [email protected])
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Abstract

Management of Leptoglossus occidentalis Heidemann in lodgepole pine (Pinus contorta var. latifolia Engelm.) seed orchards of British Columbia, Canada, would be improved with knowledge of its damage potential at different times of the growing season. Mesh insect-exclusion bags were placed over cones, and adults or nymphs of L. occidentalis were enclosed in different bags for 9 periods of 10 to 38 days between 6 May and 17 September 2004. Feeding by adult females between 6 May and 28 May reduced total extractable seeds, a result of ovule damage before fertilization. Reduction in the number of filled seeds per cone was highest between 6 May and 29 June, with each adult female reducing yield by approximately 1.7 seeds per day. Between 29 June and 10 August, each adult female reduced the number of filled seeds per cone (seed set) by 1.0 to 1.25 per day. Seed set reduction declined to approximately 0.25 filled seeds per adult female per day after 10 August. Third to fifth instars caused seed set reduction between 0.6 and 1.2 filled seeds per cone per nymph feeding day from 29 June to 10 August. Utilizing these findings would improve management of L. occidentalis in a commercial seed orchard setting.

Résumé

La gestion des Leptoglossus occidentalis Heidemann dans les pépinières à graines du pin vrillé (Pinus contorta var. latifolia Engelm.) en Colombie-Britannique serait améliorée si on connaissait leur potentiel de dommage à différents moments dans la saison de croissance. Des sacs d'exclusion en filet ont été placés sur les cônes; des adultes ou des larves de L. occidentalis ont été introduits dans des sacs différents durant 9 périodes de 10 à 38 jours entre le 6 mai et le 17 septembre 2004. L'alimentation par les femelles adultes entre le 6 mai et le 28 mai a réduit le nombre total de graines récupérables, à cause du dommage fait aux ovules avant la fécondation. La réduction du nombre de graines pleines par cône est maximale entre le 6 mai et le 29 juin, alors que chaque femelle adulte réduit le rendement par environ 1,7 graine par jour. Entre le 29 juin et le 10 août, chaque femelle adulte réduit les graines pleines de 1,0 à 1,25 graine par jour. La réduction des ensembles de graines diminue à 0,25 graine pleine par adulte femelle par jour après de 10 août. Les larves de troisième à cinquième stades causent une réduction des ensembles de graines de 0,6 à 1,2 graines pleines par jour d'alimentation de larve entre le 29 juin et le 10 août. L'utilisation de ces résultats dans le contexte d'une pépinière à graines commerciale pourrait améliorer la gestion de L. occidentalis.

[Traduit par la Rédaction]

Type
Articles
Information
The Canadian Entomologist , Volume 138 , Issue 6 , December 2006 , pp. 888 - 896
Copyright
Copyright © Entomological Society of Canada 2006

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