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TOXICITY AND RESIDUAL ACTIVITY OF FENVALERATE TO TYPHLODROMUS OCCIDENTALIS (ACARI: PHYTOSEIIDAE) AND ITS PREY TETRANYCHUS URTICAE (ACARI: TETRANYCHIDAE) ON PEAR

Published online by Cambridge University Press:  31 May 2012

Helmut Riedl  and
S. A. Hoying
Helmut Riedl
Affiliation:
Department of Entomological Sciences, University of California, Berkeley 94720
S. A. Hoying
Affiliation:
Department of Entomological Sciences, University of California, Berkeley 94720
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Abstract

Fenvalerate applied at field rates (3.4–13.7 g AI/100 L) to pear foliage in early season remained highly active to the predatory mite Typhlodromus occidentalis Nesbitt for several months until leaf drop. According to leaf disc assays, fresh deposits of fenvalerate caused considerable direct mortality but most of the later mortality was apparently caused by repellency of the residue and subsequent mite departures. Fenvalerate applied to the bark lost its contact activity more quickly than on foliage. In contrast, adult female Tetranychus urticae Koch suffered no mortality when exposed to leaf deposits, but at high dosages of fenvalerate egg laying was temporarily reduced. In slide-dip tests fenvalerate was about 5 times more toxic to T. occidentalis than to T. urticae (LC50's of 1.21 and 6.74 g AI/100 L, respectively). Our data suggest that because of the persistence of fenvalerate and the high sensitivity of T. occidentalis to this compound this predatory mite would not be able to reestablish after foliar fenvalerate applications and provide biological control of phytophagous mites.

Résumé

Le fenvalérate appliqué à des doses opérationnelles (3.4–13.7 g IA/100 L) sur du feuillage de poirier tôt en saison est resté actif vis-à-vis l'acarien prédateur Typhlodromus occidentalis Nesbitt pendant plusieurs mois jusqu'à la chute des feuilles. D'après le test du disque foliaire, des dépôts frais de fenvalérate ont causé une mortalité directe élevée, mais la mortalité subséquente est apparue dépendante de l'effet répulsif des résidus causant la fuite des acariens. Lorsqu'appliqué sur l'écorce, le fenvalérate a perdu son activité de contact plus rapidement que sur le feuillage. Au contraire, les femelles adultes de Tetranychus urticae Koch n'ont montré aucune mortalité lorsqu'exposées aux disques foliaires, mais la ponte a été réduite temporairement à fortes doses de fenvalérate. Des tests de trempage sur lamelle ont montré que le fenvalérate est environ 5 fois plus toxique pour T. occidentalis que pour T. urticae (CL50 de 1.21 et de 6.74 & IA/100 L, respectivement). Nos données indiquent qu'à cause de la persistance du fenvalérate et de la sensibilité élevée de T. occidentalis à ce produit, cet acarien prédateur ne pourrait pas réenvahir le feuillage traité au fenvalérate afin d'y agir comme auxiliaire de lutte contre l'acarien phytophage.

Type
Articles
Information
The Canadian Entomologist , Volume 115 , Issue 7 , July 1983 , pp. 807 - 813
Copyright
Copyright © Entomological Society of Canada 1983

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