Entomophaga

, Volume 25, Issue 1, pp 27–35 | Cite as

Control ofAgrotis segetum [Lep.: Noctuidae] root crops by granulosis virus

  • O. Zethner
Article

Abstract

Agrotis segetumSchiff. granulosis virus (GV) propagated in Danish laboratory cultures was applied against field populations ofA. segetum in experimental latin square plots planted with beetroots, carrots and potatoes. Some test plots were isolated by net tents extending 15 cm into the soil whereas others were not caged. Plots were treated with suspensions of GV containing 106 to 108 capsules per ml with 50 ml being applied per m2 of plot. In 4 tests in which released eggs or larvae were caged over plots, cutworm numbers and damage were reduced by approximately 80% compared to untreated plots. The comparable reductions in 3 open experiments with natural populations of cutworms were 65–75%. GV-treatment 4 days after release of eggs appeared to be more effective than treatment 10 days after release. Whereas treatments with 107 and 108 capsules per ml reduced damages to approximately 75%, the effect of 106 Capsules was only 50%.

Damage reduction by treatment with parathion varied from 50% in 2 caged experiments to approximately 20% in 2 open experiments, indicating that parathion was less effective than GV.

The data indicated a residual effect of GV from one year to the next. Furthermore GV appeared to have spread at least 10 m from foci of application.

Keywords

Cage Open Experiment Parathion Untreated Plot Cage Experiment 

Résumé

Le virus de la granulose deAgrotis segetumSchiff, multiplié en laboratoire au Danemark a été appliqué en champ contre des populations deA. segetum dans un dispositif expérimental en carré latin planté en betteraves, carottes et pommes de terre. Certaines parcelles furent protégées par des filets enfoncés jusqu'à une profondeur de 15 cm, d'autres parcelles ne furent pas recouvertes par ces cages. Les parcelles furent traitées par des suspensions de virus renfermant 106 à 108 granules par ml en utilisant 50 ml par m2. Dans 4 essais où les œufs ou les larves introduites ont été placés sous des cages, les nombres de vers gris et leurs dégâts furent réduits d'environ 80% par rapport aux parcelles non traitées. Dans 3 essais sur des populations naturelles non recouvertes, cette réduction fut de 65 à 75%. L'application du virus 4 j après le dépôt des œufs est plus efficace que le traitement 10 j après. Alors que des traitements avec 107 et 108 granules par ml réduisent les dégâts d'environ 75%, une dose de 106 granules donne seulement 50%.

La diminution des dégâts à la suite d'un traitement au parathion fut de 50% dans 2 essais sous cages et de 20% dans 2 expérimentations non protégées, ce qui montre que le parathion a été moins actif que le virus.

Un effet résiduel du virus d'une année à l'autre a été constaté; en outre le virus s'est répandu d'au moins 10 m à partir des sites où il a été appliqué.

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Copyright information

© Le François 1980

Authors and Affiliations

  • O. Zethner
    • 1
  1. 1.Zoological InstituteRoyal Veterinary and Agricultural UniversityCopenhagenDenmark

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