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Unexpectedly high levels of parasitism of wheat stem sawfly larvae in postcutting diapause chambers

Published online by Cambridge University Press:  07 September 2012

Tatyana A. Rand ,
Debra K. Waters  and
Thomas G. Shanower
Tatyana A. Rand*
Affiliation:
United States Department of Agriculture, Agricultural Research Service, Northern Plains Agricultural Research Laboratory, Sidney, MT 59270, United States of America
Debra K. Waters
Affiliation:
United States Department of Agriculture, Agricultural Research Service, Northern Plains Agricultural Research Laboratory, Sidney, MT 59270, United States of America
Thomas G. Shanower
Affiliation:
United States Department of Agriculture, Agricultural Research Service, Center for Grain and Animal Health Research, Manhattan, KS 66502, United States of America
*
1Corresponding author (e-mail: tatyana.rand@ars.usda.gov).
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Abstract

We examined rates of late-season parasitism of larvae of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), by native species of Bracon F. (Hymenoptera: Braconidae) over 8 years in Montana and North Dakota, United States of America. We found that rates of parasitism of larvae in diapause chambers reached a maximum of 46%, exceeding the previously reported maximum of 2.5% in 75% of sites and years examined. In contrast to previous work, our results demonstrate that C. cinctus larvae are suitable hosts for braconid parasitoids, even after the formation of diapause chambers, and suggest that parasitism rates may be underestimated if stems are sampled prior to harvest.

Résumé

Nous examinons les taux de parasitisme en fin de saison chez les larves du cèphe du blé, Cephus cinctus Norton (Hymnenoptera: Cephidae), par les espèces indigènes de Bracon F. (Hymenoptera: Braconidae) sur une période de 8 ans dans le Montana et le Dakota du Nord, États-Unis. Les taux de parasitisme des larves en diapause dans leur logette atteignent un maximum de 46 %, ce qui dépasse le maximum de 2,5 % enregistré antérieurement dans 75 % des sites et années examinés. Contrairement aux travaux précédents, nos résultats démontrent que les larves de C. cinctus sont des hôtes appropriés pour les parasitoïdes braconidés, même après la formation des logettes de diapause; il se peut que les taux de parasitisme aient été sous-estimés par le prélèvement des tiges avant la période des récoltes.

[Traduit par la Rédaction]

Type
Research Article
Information
The Canadian Entomologist , Volume 143 , Issue 5 , September 2011 , pp. 455 - 459
Copyright
Copyright © Entomological Society of Canada 2011

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