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REGIONAL RESISTANCE TO INSECTICIDES IN PSYLLA PYRICOLA FROM PEAR ORCHARDS IN OREGON1

Published online by Cambridge University Press:  31 May 2012

P.A. Follett ,
B.A. Croft  and
P.H. Westigard
P.A. Follett
Affiliation:
Department of Entomology, Oregon State Univenity, Corvallis, OR 97331
B.A. Croft
Affiliation:
Department of Entomology, Oregon State Univenity, Corvallis, OR 97331
P.H. Westigard
Affiliation:
Department of Entomology, Oregon State Univenity, Corvallis, OR 97331
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Abstract

Using a slide-dip bioassay, Psylla pyricola Forester from intensively sprayed, minimally sprayed (IPM), recently abandoned, and long-abandoned pear orchards in the Hood River, Rogue River, and Willamette valleys of Oregon were surveyed for resistances to azinphosmethyl, endosulfan, Perthane®, and fenvalerate. Lethal-concentration (LC50) values showed resistance levels from 12- to 41-fold to azinphosmethyl and 5- to 12-fold for endosulfan in selected populations. Resistance patterns did not correlate with orchard-treatment histories in the Hood River and Rogue River valleys, where even long-abandoned orchards harbored resistance psylla. There was better association between treatment histories and resistance levels in populations from the more widely scattered orchards in the Willamette Valley. A regional analysis of mean LC50 values indicated that psylla resistance was significantly higher to azinphosmethyl in the Rogue River Valley and to endosulfan in the Hood River Valley. Regional resistance levels for these compounds reflect differences in intensity of past use. A regional hypothesis is proposed to explain the patterns of resistance developed in the Hood River and Rogue River Valleys, where pear production is intensive as opposed to the more localized patterns of resistance in the Willamette Valley. Applications of results to the management of resistance are discussed.

Résumé

On a étudié la résistance de Psylla pyricola Forester à l'azinphosméthyl, l'endosulfan, le Perthane® et le fenvalerate, dans des vergers de poiriers qui étaient soit intensivement arrosés, arrosés au minimum (LI), récemment abandonnés ou abandonnés depuis long-temps, dans les vallées de Willamette, de Hood River et de Rogue River, en utilisant le test de l'immersion sur lame microscopique. Les CL50 de populations choisies ont révélé des facteurs de résistance de 12 à 41 fois pour l'azinphosméthyl et de 5 à 12 fois pour l'endosulfan. La résistance n'était pas corrélée avec l'historique d'arrosage des vergers dans les vallées de Hood River et de Rogue River, où même des vergers abandonnés depuis longtemps hébergeaient des psylles résistants. On a observé une meilleure corrélation entre l'historique des traitements et la résistance dans les vergers plus dispersés de la vallée de Willamette. L'analyse régionale des CL50 a indiqué que le psylle était plus résistant à l'azinphosméthyl dans la vallée de Rogue River, et à l'endosulfan dans la vallée de Hood River. Les niveaux de résistance régionale pour ces produits reflètent des différences d'intensité de leur utilisation. On propose une hypothèse régionale pour expliquer les patrons de résistance apparus dans les vallées de Hood River et de Rogue River, où la culture du poirier est intensive, contrairement aux patrons de résistance plus localisés de la vallée de Willamette. On discute de l'application de ces résultats à la régie de la résistance.

Type
Articles
Information
The Canadian Entomologist , Volume 117 , Issue 5 , May 1985 , pp. 565 - 573
Copyright
Copyright © Entomological Society of Canada 1985

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