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AN ACTION THRESHOLD FOR CONTROL OF LEPIDOPTEROUS PESTS OF CABBAGE IN PRINCE EDWARD ISLAND

Published online by Cambridge University Press:  31 May 2012

Andrew P. Dornan
Affiliation:
Agriculture Canada Research Station, Box 1210, Charlottetown, Prince Edward Island, Canada C1A 7M8
Jeff G. Stewart
Affiliation:
Agriculture Canada Research Station, Box 1210, Charlottetown, Prince Edward Island, Canada C1A 7M8
Mark K. Sears
Affiliation:
Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1

Abstract

Action thresholds for imported cabbageworm, Pieris rapae (L.), diamondback moth, Plutella xylostella (L.), and cabbage looper, Trichoplusia ni (Hübner), were evaluated on two cultivars of cabbage, Brassica oleracea var. capitata (L.), in Prince Edward Island. Thresholds were tested on plots of mid-season cabbage, cv. Minicole, and late-season cabbage, cv. Lennox, both grown for fresh market in 1991 and 1992. Management of larval populations at a threshold of 0.25 Cabbage Looper Equivalents (CLE) per plant resulted in yields equal to those obtained with bi-weekly applications or grower treatments. Higher thresholds of 0.50 and 1.0 CLE per plant were not as useful and did’ not consistently result in yields greater than untreated plots. Use of the threshold of 0.25 CLE per plant reduced the number of applications of insecticides by 30% compared with spraying insecticide at bi-weekly intervals from heading to harvest, and 43% compared with management by the grower without regard to insect populations or growth stage of the crop.

Résumé

Les seuils d’efficacité de la Piéride du chou, Pieris rapae (L.), de la Fausse-teigne des crucifères, Plutella xylostella (L.) et de la Fausse-arpenteuse du chou, Trichoplusia ni (Hübner), ont été évalués sur deux cultivars du chou Brassica oleracea var. capitata (L.) dans l’île-du-Prince-Édouard. Les concentrations seuils ont été éprouvées dans des cultures de chou de mi-saison, cv. Minicole, et de fin de saison, cv. Lennox, deux cultures destinées à la mise en marché en 1991 et 1992. Le contrôle des populations de larves à une concentration seuil de 0,25 équivalent de Fausse-arpenteuse du chou (CLE) par plant a donné lieu à des récoltes égales à celles obtenues après arrosage bi-hebdomadaire d’insecticide ou après traitement mis au point par le cultivateur. Les concentrations plus élevées de 0,50 et 1,0 CLE par plant ne se sont pas avérées aussi utiles et n’ont pas toujours donné de meilleures récoltes que celles obtenues dans les cultures non traitées. L’utilisation d’une concentration seuil de 0,25 CLE par plant a réduit le nombre d’applications d’insecticides de 30% par rapport aux traitements par arrosage bi-hebdomadaire d’insecticide entre la sortie de terre et la récolte, et de 43% par rapport aux traitements utilisés par le cultivateur qui ne tiennent compte ni des populations d’insectes, ni du stade de croissance de la récolte.

[Traduit par la Rédaction]

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1994

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