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TOXICITY OF DIFLUBENZURON TO NYMPHS OF THE MIGRATORY GRASSHOPPER, MELANOPLUS SANGUINIPES (ORTHOPTERA: ACRIDIDAE)

Published online by Cambridge University Press:  31 May 2012

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

Abstract

Laboratory tests showed that nymphs of the migratory grasshopper are very sensitive to diflubenzuron (Dimilin) when reared continuously on treated wheat seedlings or artificial diet and fresh lettuce. At concentrations of 10 ppm or above, diflubenzuron completely inhibited moulting of 2nd-instar nymphs. With continuous exposure on treated wheat seedlings, the LC90 values after 8, 12 and 20 days were 10.0, 2.4 and 0.8 ppm, respectively. Comparable values were obtained with the artificial diet and lettuce. However, when 2nd instars were placed on diflubenzuron-treated wheat foliage for 1 day then transferred onto untreated plants, toxicity declined markedly.

Although the toxic effects of diflubenzuron were delayed, dry weight determinations on wheat seedlings indicated that nymphal feeding damage was insignificant if the plants had been sprayed with 10 ppm diflubenzuron.

The implications of these findings are discussed in terms of the potential field use of diflubenzuron against stationary and mobile grasshopper nymphs.

Résumé

Des tests de laboratoire ont montré que les larves du criquet migrateur sont très sensibles au diflubenzuron (Dimilin) lorsqu'élevées de façon continue sur des plantules de blé ou du régime artificiel avec de la laitue traités. A des concentrations de 10 ppm ou plus, le diflubenzuron a inhibé complètement la mue de larves de stade 2. Les valeurs de la CL90 après 8, 12 et 20 jours d'exposition continue sur des plantules de blé traités ont été respectivement de 10.0, 2.4 et 0.8 ppm. Des valeurs semblables ont été obtenues avec le régime artificiel accompagné de laitue. Cependant, lorsque des stades 2 ont été placés sur du feuillage de blé traité pour 1 journée et ensuite transférés sur des plants non traités, la toxicité a baissé de beaucoup.

Bien que les effets toxiques du diflubenzuron soient survenus après un délai, des mesures de poids sur des plantules de blé ont montré que la défoliation n'était pas importante lorsque les plants étaient traités avec 10 ppm de diflubenzuron.

Les implications de ces observations sont commentées en regard du potentiel d'utilisation du diflubenzuron contre les larves mobiles et sédentaires des acridiens.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1982

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