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Toxicity of the Botanical Insecticide Ryania speciosa to Culex pipiens fatigans Wied.*

Published online by Cambridge University Press:  10 July 2009

L. J. Charles
L. J. Charles
Affiliation:
Chief Officer, Mosquito Control Service, Medical Department, British Guiana.
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Extract

In the course of general studies on control of Culex pipiens fatigans Wied. in British Guiana, the indigenous shrub Ryania speciosa, proven to possess insecticidal activity against certain agricultural pests, was investigated.

Aqueous extracts of the dried stem were shown to possess toxic properties against all larval stages of C. pipiens fatigans under clean laboratory conditions. Under conditions simulating a water-logged pit latrine, however, toxicity was greatly reduced by adsorption of the active agent ryanodine, rendering the crude stem relatively ineffective after 16 days. Because of the great bulk of unprocessed material required for even this limited result in pit latrines—which constitute an important local problem—Ryania was not considered of practical value in C. pipiens fatigans control.

Aqueous and alcoholic extracts of Ryania speciosa had no contact insecticidal properties against adults of this species.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 45 , Issue 2 , June 1954 , pp. 403 - 410
Copyright
Copyright © Cambridge University Press 1954

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