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EXPLOITING COLD-HARDINESS TO SEPARATE PISSODES STROBI (PECK) (COLEOPTERA: CURCULIONIDAE) FROM ASSOCIATED INSECTS IN LEADERS OF PICEA SITCHENSIS (BONG.) CARR.

Published online by Cambridge University Press:  31 May 2012

Michael A. Hulme
Affiliation:
Canadian Forestry Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
Allan F. Dawson
Affiliation:
Canadian Forestry Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5
John W.E. Harris
Affiliation:
Canadian Forestry Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, Canada V8Z 1M5

Abstract

The cold-hardiness of Pissodes strobi (Peck) and of its insect associates in leaders of Picea sitchensis (Bong.) Carr. was tested to determine whether the insect associates could be retrieved free of P. strobi for use in biological control attempts on P. strobi. Leaders were stored at −8, −16, or −26°C for periods from 1 to 14 days. All P. strobi were dead after 14 days at −16°C, whereas their dipteran predator, Lonchaea corticis Taylor, and hymenopteran parasites, Eurytoma pissodis Girault and Rhopalicus pulchripennis (Crawford), continued development after storage at −26°C. The scarcer Dolichomitus terebrans (Ratzeburg) (Ichneumonidae) survived similarly although we did not always find it in our samples; and the equally scarce Bracon pini (Muesebeck) (Braconidae) seemed susceptible to −26°C but continued development at −16°C. Of the few Allodorus crassigaster (Provancher) (Braconidae) obtained one adult emerged after 7 days at −16°C. These results show that in leader clipping operations now used for attempted control of P. strobi, most of the insect associates could be retrieved from the leaders after suitable cold treatment. Additional tests showed that cold-treated leaders could be stored outdoors in temperatures at least down to −20°C with little effect on adult emergence of insect associates. The field testing also showed that few P. strobi in leaders of P. sitchensis can survive overnight temperatures near −20°C.

Résumé

Nous avons étudié la résistance au froid de Pissodes strobi (Peck) et des insectes avec lesquels it est associé dans les pousses apicales de Picea sitchensis (Bong.) Carr. afin de déterminer si les insectes associés pouvaient être extraits sans P. strobi pour des essais de répression biologique sur celui-ci. Les pousses ont été gardées à −8, −16 ou −26°C pendant des périodes variant de 1 à 14 jours. Après 14 jours à −16°C, tous les P. strobi étaient morts. Par contre, leur prédateur diptère Lonchaea conicis Taylor et leurs parasites hyménoptères Eurytoma pissodis Girault ainsi que Rhopalicus pulchripennis (Crawford) ont poursuivi leur développement après des séjours à −26°C. On a observé une survie similaire de Dolichomitus terebrans (Ratzeburg) (Ichneumonidae), qui est plus rare et que nous n’avons pas toujours trouvé dans nos échantillons. Quant à Bracon pini (Muesebeck) (Braconidae), auire espèce rare, il a semblé vulnérable à une température de −26°C mais a poursuivi son développement après les séjours à −16°C. Des quelques Allodorus crassigaster (Provancher) (Braconidae) obtenus, un seul adulte s’est développé après 7 jours à −16°C. Ces résultats indiquent que des pousses apicaies coupées dans le cadre des opérations de lutte contre P. strobi, il est possible d’extraire la plupart des insectes associés à celui-ci après un traitement approprié au froid. D’autres tests ont révélé que les pousses traitées au froid pouvaient être gardées à l’extérieur à des températures atteignant −20°C au moins sans que des effets importants soient observés sur l’émergence des adultes chez les insectes associés à P. strobi. Les tests à l’extérieur ont également indiqué que peu de P. strobi dans les pousses apicales de P. sitchensis peuvent survivre quand la température pendant la nuit atteint près de −20°C.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1986

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