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INFESTATION OF CERATOCYSTIS WAGENERI-INFECTED PONDEROSA PINES BY BARK BEETLES (COLEOPTERA: SCOLYTIDAE) IN THE CENTRAL SIERRA NEVADA

Published online by Cambridge University Press:  31 May 2012

D. J. Goheen
Affiliation:
Department of Plant Pathology, University of California, Berkeley 94720
F. W. Cobb Jr.
Affiliation:
Department of Plant Pathology, University of California, Berkeley 94720

Abstract

The relationship between bark beetle infestation of ponderosa pine and severity of infection by Ceratocystis wageneri was investigated by closely monitoring 256 trees (136 apparently healthy, 60 moderately diseased, and 60 severely diseased at initiation of study) for beetle infestation from summer 1972 to fall 1975. Disease ratings were updated by periodic examination, and some trees changed disease category during the study. Ninety trees were infested by Dendroctonus brevicomis, D. ponderosae, or both, five by buprestids alone, and one tree died from effects of the pathogen alone. Sixty-two of the beetle-infested trees were severely diseased at time of infestation, 25 were moderately diseased, and only three were apparently healthy. Thus, the results showed that bark beetles were much more likely to infest infected than healthy trees. Among diseased trees, those with advanced infections were most likely to be infested. There was evidence that buprestids (especially Melanophila spp.) and possibly Ips spp. attacked diseased trees prior to Dendroctonus spp. infestation.

Résumé

La relation entre l’attaque du pin ponderosa par les scolytes et les buprestes, et l’infection causée par Coratocystis wageneri a été étudiée en surveillant de près 256 arbres (136 apparemment sains, 60 modérément infectés et 60 sévèrement infectés au début de l’étude) pour la présence de ces coléoptères, de l’été 1972 à l’automne 1975. L’indice d’infection des arbres suivis a été remis à jour par des examens périodiques, et certains arbres ont changé de catégorie au cours de l’étude. Quatre vingt dix arbres ont été infestés par Dendroctonus brevicomis, D. ponderosae, ou les deux, cinq par des buprestes seulement, et un arbre est mort des effets du pathogène seul. Parmi les arbres infestés par les coléoptères, 62 étaient sévèrement malades au moment de l’infestation, 25 étaient modérément malades, et seulement 3 étaient apparemment sains. Les résultats indiquent donc que les coléoptères ont montré une nette tendance à s’attaquer à des arbres infectés plutôt qu’à des arbres sains. Parmi les arbres malades, ceux montrant une infection avancée se sont avérés les plus susceptibles d’être infestés. Certaines observations indiquent que des buprestes (particulièrement Melanophila spp.) et possiblement des Ips spp. avaient déjà attaqué les arbres malades avant leur infestation par les Dendroctonus spp.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1980

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