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DEVELOPMENT OF NUCLEAR POLYHEDROSIS VIRUS FOR CONTROL OF GYPSY MOTH (LEPIDOPTERA: LYMANTRIIDAE) IN ONTARIO. II. REDUCTION IN DOSAGE AND EMITTED VOLUME (1989 AND 1990)

Published online by Cambridge University Press:  31 May 2012

J.C. Cunningham
Affiliation:
Forestry Canada, Forest Pest Management Institute, PO Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7
W.J. Kaupp
Affiliation:
Forestry Canada, Forest Pest Management Institute, PO Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7
R.A. Fleming
Affiliation:
Forestry Canada, Forest Pest Management Institute, PO Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7
K.W. Brown
Affiliation:
Forestry Canada, Forest Pest Management Institute, PO Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7
T. Burns
Affiliation:
Forestry Canada, Forest Pest Management Institute, PO Box 490, Sault Ste. Marie, Ontario, Canada P6A 5M7

Abstract

A double application of 1.25 × 1012 (total 2.5 × 1012) polyhedral inclusion bodies (PIB) of Disparvirus (nuclear polyhedrosis virus) in an emitted volume of 10.0 L per ha gave acceptable control of gypsy moth, Lymantria dispar (L.), larvae in 1988. More aerial spray trials were conducted in 1989 and 1990 to test a reduced dosage and volume of Disparvirus. Dosage on all plots, applied when larvae were mainly in their first instar, was a double treatment of 5 × 1011 PIB per ha, 3–5 days apart, giving a total of 1012 PIB per ha. The aqueous tank mix contained 25% (v/v) molasses, 10% (w/v) Orzan LS, and 2% (v/v) Rhoplex B60A sticker. Emitted volumes of 10.0 L per ha and 5.0 L per ha were each tested on three replicated plots in 1989, and 5.0 L per ha and 2.5 L per ha were each tested on three replicated plots in 1990. In both 1989 and 1990, three untreated check plots were paired with treated plots on the basis of pre-spray egg-mass densities.The treatments were assessed by counts of pupae in burlap traps, estimates of defoliation, and change in numbers of egg masses in the treated and check plots. Better control was obtained with the reduced dosage at 10.0 L per ha and 5.0 L per ha than at 2.5 L per ha. Using the aqueous formulation described above, a double application of 5 × 1011 PIB per ha at 5.0 L per ha applied at the peak of the first larval instar is the current recommendation for control of gypsy moth in Ontario using nuclear polyhedrosis virus.

Résumé

Une double application de 1,25 × 1012 (au total 2,5 × 1012) inclusions polyèdres (PIB) du Disparvirus (virus de la polyédrose nucléaire) dans un volume émis de 10,0 L par hectare avait donné des résultats satisfaisants au cours d’une tentative de contrôle des larves de la Spongieuse, Lymantria dispar (L.), en 1988. D’autres applications aériennes ont été tentées en 1989 et 1990 pour tester des réductions de dose et de volume de Disparvirus dans les solutions vaporisées. Sur chaque grille-échantillon, deux traitements de 5 × 1011 PIB par ha ont été appliqués à 3–5 jours d’intervalle, donc 1012 PIB par ha au total, au moment où la plupart des larves étaient au premier stade. La solution aqueuse vaporisée contenait 25% (v/v) de mélasse, 10% (m/v) d’Orzan LS et 2% (v/v) de Rhoplex B60A, une substance adhésive. Des volumes de 10,0 L par hectare et de 5,0 L par hectare ont été vaporisés sur trois grilles-échantillons identiques en 1989 et des volumes de 5,0 L par ha et de 2,5 L par hectare, sur trois grilles-échantillons identiques en 1990. Les 2 années, trois grilles-échantillons témoins non traitées ont été appariées aux grilles traitées, d’après la densité des masses d’oeufs présentes avant le traitement.L’efficacité des traitements a été mesurée en comptant le nombre de chrysalides présentes dans des pièges de jute, en estimant la défoliation et en comparant le nombre de masses d’oeufs dans les grilles traitées et les grilles témoins. Une dose réduite dans une émission de 10,0 L par ha ou de 5,0 L par ha donne de meilleurs résultats qu’une dose réduite dans une émission de 2,5 L par ha. Pour contrôler les épidémies de Spongieuses en Ontario au moyen du virus de la polyédrose nucléaire, nous recommandons l’utilisation de la solution aqueuse décrite ci-haut, appliquée en deux fois, à raison de 5 × 1011 PIB par ha dans 5,0 L chaque fois, au moment où la majorité des larves sont au premier stade.

[Traduit par la rédaction]

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1993

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