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DISTRIBUTION AND IMPACT OF LEPTOGLOSSUS OCCIDENTALS HEIDEMANN (HEMIPTERA: COREIDAE) IN SEED ORCHARDS IN BRITISH COLUMBIA

Published online by Cambridge University Press:  31 May 2012

Suzie E. Blatt
Affiliation:
Centre for Pest Management, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
John H. Borden
Affiliation:
Centre for Pest Management, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6

Abstract

Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) is considered to be an important cone and seed pest in seed orchards in British Columbia; however, no impact studies have been done in Canada. Surveys to determine the distribution of L. occidentalis were conducted over a 3-year period in three coastal seed orchards of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and over a 2-year period in two seed orchards of lodgepole pine, Pinus contorta var. latifolia Engelmann. Leptoglossus occidentalis was found to distribute itself in patches, coinciding with a clonal preference. Seed losses were assessed for 2 years in the coastal Douglas-fir orchards and for 1 year in one lodgepole pine orchard. The percentages of partially filled seed that could have been caused by feeding of L. occidentalis or by a number of other factors were < 5% in coastal Douglas-fir for both 1992 and 1993 and ~14% in lodgepole pine in 1993. Apparently because populations of L. occidentalis were low, there was no correlation between the percentage of partially filled seed and number of insects per tree. Except in unusual circumstances, management measures in Canada are judged not to be necessary as populations of L. occidentalis are consistently below the calculated threshold levels required to cause ≥5% loss in seed production.

Résumé

Leptoglossus occidentalis Heidemann (Hemiptère : Coreidae) est considéré être un important ravageur des cônes et des graines des vergers à graines de la Colombie-Britannique; aucune étude d’impact n’a cependant été effectuée au Canada. Des vergers ont été étudiés sur une période de 3 ans afin de déterminer la distribution de L. occidentalis dans trois vergers à graines de la variété côtière du Douglas taxifolié, Pseudotsuga menziesii (Mirb.) Franco, et sur une période de 2 ans dans deux vergers à graines du pin tordu, Pinus contorta var. latifolia Engelmann. Les auteurs ont trouvé que L. occidentalis se distribue en groupes, correspondant à une préférence clonale. Les pertes en graines ont été évaluées pendant 2 ans dans les vergers à graines du Douglas taxifolié et pendant 1 an dans un verger de pin tordu. Les pourcentages de graines partiellement remplies qui pourraient être attribués à l’activité trophique de L. occidentalis ou à d’autres facteurs étaient < 5% pour le douglas taxifolié en 1992 et en 1993, et ~14% pour le pin tordu en 1993. Aucune corrélation n’a été trouvée entre le pourcentage de graines partiellement remplies et le nombre d’insectes par arbre, apparemment dû au fait que les populations de L. occidentalis étaient faibles. De plus, des mesures particulières de gestion ne sont pas jugées nécessaires au Canada, sauf dans des circonstances inhabituelles, puisque les populations de L. occidentalis sont sans exception sous les seuils requis pour causer des pertes de production de graines ≥5%.

[Traduit par la Rédaction]

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1996

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