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SUSCEPTIBILITY OF SOME FOREST INSECTS TO MIXTURES OF COMMERCIAL BACILLUS THURINGIENSIS AND CHEMICAL INSECTICIDES, AND SENSITIVITY OF THE PATHOGEN TO THE INSECTICIDES

Published online by Cambridge University Press:  31 May 2012

Oswald N. Morris
Affiliation:
Chemical Control Research Institute, Canadian Forestry Service, Ottawa

Abstract

Experiments were designed to determine the effects of low doses of some insecticides on the viability and physiological characteristics of commercial Bacillus thuringiensis (Berliner) as a prelude to studies on the susceptibility of lepidopterous forest defoliators to mixtures of bacteria and insecticides.

The results show that the insecticides tested had no effect on viability or physiological integrity of the bacteria.

Bacteria–insecticide combination effects varied from strongly antagonistic to strongly supplemental depending on insecticide or Thuricide® formulations and concentrations and on the relative susceptibility of the test species to either agent applied separately. Pyrethrum at 10−3 was highly potentiating to BT at 10−1 against third instar Halisidota argentata. Among Hyphantria cunea, a supplemental effect always resulted from combining Thuricide® at 10−2 with low concentrations of malathion, phosphamidon, or pyrethrum.

There was generally a drastic reduction in feeding activity among BT-treated insects and a further reduction among BT-chemical-insecticide-treated ones compared with controls.

Résumé

Expériences destinées à déterminer les effets de quelques insecticides à faibles doses sur la viabilité et les caractéristiques physiologiques de la Bactérie commerciale Bacillus thuringiensis (BT), comme prélude à des études sur la sensibilité des Lepidoptères associés à la défoliation des arbres forestier aux mélanges de Bactéries et d’insecticides.

Absence d’effets, d’après les résultats, des insecticides expérimentés sur la viabilité ou l’intégrité physiologique des Bactéries.

Variabilité de fortement antagonistes à fortement adjuvants des effets des combinaisons de Bactéries et d’insecticides, selon les formules et les concentrations d’insecticides ou de Thuricide® et la sensibilité relative des espèces éprouvées à l’un ou l’autre agent appliqué séparément. Renforcement marqué de BT à 10−1 par le pyrethrum à 10−3 contre Halisidota argentata au 3e âge larvaire. Effet renforcé contre Hyphantria cunea constant en combinant Thuricide® à 10−2 avec de faibles doses de malathion, phosphamidon ou pyrethrum.

Réduction drastique de l’activité nutricielle en général chez les insectes traités au BT, mais encore plus poussée chez ceux soumis aux combinaisons BT-insecticides chimiques, par rapport aux sujets témoins.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1972

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