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FACTORS INFLUENCING THE ACTIVITY OF DIFLUBENZURON AGAINST THE CODLING MOTH, LASPEYRESIA POMONELLA (LEPIDOPTERA: OLETHREUTIDAE)

Published online by Cambridge University Press:  31 May 2012

R. H. Elliott
Affiliation:
Department of Plant Science, University of British Columbia, Vancouver V6T 2A2
D. W. Anderson
Affiliation:
Department of Plant Science, University of British Columbia, Vancouver V6T 2A2

Abstract

Codling moth eggs were very sensitive to diflubenzuron (Dimilin), particularly when treated topically shortly after oviposition. Regression analysis showed a linear relationship between % hatch and the age at which the eggs were treated with diflubenzuron. The LC50 values for 0- to 21/2- and 3-day-old eggs were 1.1 and 17.2 ppm, respectively. Egg hatch was also inversely related to the length of time the chorion was in contact with the diflubenzuron solution. When the compound had dried on fruit or foliage, residual activity against the eggs was excellent and did not decrease markedly over a 10-day period. The surfactant, Tween 20, enhanced the contact ovicidal activity of diflubenzuron especially on older eggs. Tween 20 also improved the residual activity of diflubenzuron on foliage and immature apples but not waxy mature apples.

Diflubenzuron incorporated into artificial diet was toxic to 1st- and 2nd-instar larvae. The LC50s for the two instars were 48.2 and 8.1 ppm, respectively. When 1st instars fed on diflubenzuron + Tween 20-treated foliage for 2 days, larval entry into apples was not impaired but subsequent larval survival was reduced significantly. However, neither fruit entry nor larval survival was affected when 1st instars were reared on apples which had been dipped in 500 ppm diflubenzuron - Tween 20. Adult codling moths dipped in or fed diflubenzuron solutions showed no marked adverse effects although marginal reductions in egg viability were observed.

Résumé

Les oeufs du carpocapse de la pomme se sont avérés très sensibles au diflubenzuron (Dimilin), spécialement lorsque traités topicalement peu après la ponte. La régression a montré l'existence d'une relation linéaire entre le pourcentage d'éclosion et l'âge auquel les oeufs étaient traités. Les valeurs observées de la CL50 pour des oeufs âgés de 0 à 21/2 et 3 jours sont de 1.1 et 17.2 ppm, respectivement. L'incidence d'éclosion s'est montrée inversement liée à la durée de contact du chorion avec la solution de diflubenzuron. L'activité résiduelle du produit une fois séché sur le fruit ou le feuillage a été excellente, et n'a pas baissé de façon marquée sur une période de 10 jours : Le surfactant Tween 20 a augmenté l'activité ovicide de contact du diflubenzuron, spécialement sur les oeufs les plus âgés. Le Tween 20 a aussi augmenté l'activité résiduelle du diflubenzuron sur le feuillage et les pommes vertes, mais pas sur les pommes mûres dont la surface est cireuse. Le diflubenzuron s'est avéré toxique pour les larves des stades 1 et 2 lorqu'incorporé à un régime artificiel. Les CL50 mesurées étaient 48.2 et 8.1 ppm, respectivement.. L'alimentation de stades 1 à partir de feuillage traité au diflubenzuron + Tween 20 pendant 2 jours n'a pas empêché la pénétration des larves dans les pommes, mais a réduit significativement leur survie par la suite. Cependant, aucun effet sur la pénétration dans le fruit ni sur la survie larvaire n'a été observé lorsque des stades 1 ont été élevés sur des pommes qui avaient trempé dans le diflubenzuron-Tween 20 à 500 ppm. Des papillons du carpocapse plongés dans, ou nourris de solutions de diflubenzuron n'ont montré aucun effet adverse notable, bien que des réductions marginales de la viabilité des oeufs aient été observées.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1982

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