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DISPLACEMENT OF BATHYPLECTES CURCULIONIS (THOMS.) (HYMENOPTERA: ICHNEUMONIDAE) BY B. ANURUS (THOMS.) IN EASTERN ONTARIO POPULATIONS OF THE ALFALFA WEEVIL, HYPERA POSTICA (GYLL.) (COLEOPTERA: CURCULIONIDAE)

Published online by Cambridge University Press:  31 May 2012

D.G. Harcourt
D.G. Harcourt
Affiliation:
Plant Research Centre, Agriculture Canada, Ottawa, Ontario, Canada K1A 0C6
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Abstract

Bathyplectes anurus (Thoms.) has displaced B. curculionis (Thorns.) as the main larval parasitoid in populations of the alfalfa weevil, Hypera postica (Gyll.), in eastern Ontario. Following its belated spread to the Bay of Quinte dairy belt, it used a combination of r and K strategies to assert its superiority: a greater reproductive capacity, more rapid search and handling, and more aggressive behaviour. Also, it is not subject to encapsulation by the host and reduces direct competition with the entomopafhogenic fungus Zoophthora phytonomi (Arthur) by laying its eggs in older hosts that have a greater probability of escaping death from disease. Taken together, these factors have enabled it to perform better than B. curculionis and to displace it in the host–parasitoid community. Moreover, it may have the potential to stabilize weevil populations during years when the fungus is enzootic.

Résumé

Bathyplectes anurus (Thoms.) a déplacé B. curculionis (Thoms.) comme parasitoïde larvaire principal aux populations du charançon postiche de la lucerne, Hypera postica (Gyll.), dans l’est de l’Ontario. Suite à sa diffusion tardive à la zone laitière de la Baie de Quinte, il a utilisé une combinaison de stratégies de r et K pour faire valoir sa supériorité : une capacité réproductrice plus grande, la recherche et le traitement plus rapide, et un comportement plus aggressif. Aussi, il n’est pas assujetti d’être enclos par l’hôte et la compétition directe avec le champignon entomopathogénique Zoophthora phytonomi (Arthur) est réduite à cause que la ponte dans les hôtes âgés permet aux oeufs une plus grande possibilité d’échapper à la mort occasionnée par la maladie. Pris dans l’ensemble, ces éléments ont donné le pouvoir de mieux s’acquitter que B. curculionis et de le déplacer dans la communauté hôte–parasitoïde. De plus, il pourrait avoir le potentiel pour stabiliser les populations de charançon pendant les années où le champignon est enzootique.

Type
Articles
Information
The Canadian Entomologist , Volume 122 , Issue 4 , August 1990 , pp. 641 - 645
Copyright
Copyright © Entomological Society of Canada 1990

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