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Rhinocyllus conicus Establishment for Biocontrol of Thistles in Virginia

Published online by Cambridge University Press:  12 June 2017

W. W. Surles ,
L. T. Kok  and
R. L. Pienkowski
W. W. Surles
Affiliation:
Dep. of Entomol., Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
L. T. Kok
Affiliation:
Dep. of Entomol., Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
R. L. Pienkowski
Affiliation:
Dep. of Entomol., Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
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Abstract

Rhinocyllus conicus Froel. (Col.: Curculionidae) larvae feeding within the capitula of Carduus thistles may reduce production of viable seeds. Each R. conicus larva destroyed 9.7 developing musk thistle (Carduus nutans L.) seeds. An average musk thistle capitulum, 29.2 mm diameter, produced 15.3 viable achenes per millimeter of diameter for an average of 447 viable seeds. Surveys of 23 release sites in Virginia revealed that thistles at 12 had sustained a population of weevils. Weevil eggs at six sites have increased in abundance, and establishment appears assured. Colonization of R. conicus was enhanced by spring or early summer releases; larger stocks of insects were required for late summer releases. The weevils exhibited better synchronization with musk thistle than with plumeless thistle (Carduus acanthoides L.); and best success has been achieved where extensive, persistent stands of musk thistle were available.

Type
Research Article
Information
Weed Science , Volume 22 , Issue 1 , January 1974 , pp. 1 - 3
Copyright
Copyright © 1974 by the Weed Science Society of America 

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References

Literature Cited

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