An evaluation of two strains of Cyrtobagous salviniae Calder and Sands as natural enemies of the aquatic weeds salvinia molesta Mitchell and Salvinia minima Baker

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Title: An evaluation of two strains of Cyrtobagous salviniae Calder and Sands as natural enemies of the aquatic weeds salvinia molesta Mitchell and Salvinia minima Baker
Author: Dye, Jeremiah M.
Abstract: The floating aquatic weeds common salvinia (Salvinia minima Baker ) and giant salvinia (Salvinia molesta Mitchell ) degrade aquatic systems through fast , mat forming growth . The Salvinia specialist weevil Cyrtobagous salviniae Calder and Sands has been used to reduce the severity of giant salvinia infestations and associated with reduced severity of common salvinia infestations . Genetically , morphologically and biologically distinct strains of C . salviniae exist , but their relative potential for success as biological control agents of Salvinia species has not been evaluated . This thesis (1 ) describes a recirculating water system designed for conducting such studies and (2 ) reports the results of C . salviniae strain comparisons . A recirculating water system with a high degree of replication and minimal variation in water flow , temperature and light intensity was used for laboratory experiments using sixty -day temperature profiles averaging 31 .4 , 26 .5 and 8 .0 ?C derived from surface water temperatures measured at lakes in expected range of Salvinia species in the North America . Larval and adult population numbers of two C . salviniae strains (Australia and Florida ) were determined for each temperature profile along with feeding induced plant necrosis on both Salvinia species . Australia C . salviniae had lower survivorship rates to adulthood on common salvinia than did Florida C . salviniae at the 31 .4 and 26 .5 ?C temperature profiles . Neither strain reproduced , and no significant between -strain differences in plant necrosis were detected at the 8 .0 ?C temperature profile . At 31 .4 ?C there were no significant differences in adult counts , larval counts or plant damage between the two strains on giant salvinia . At 26 .5 ?C , however , significantly fewer larvae were collected from initially released adults and significantly less plant necrosis was associated with weevil feeding by Florida strain compared to Australia strain weevils . These results may have arisen from comparing Australia weevils from a growing colony to Florida weevils from a declining colony . Overall , the results indicate that only Florida C . salviniae should be released against common salvinia . Florida C . salviniae may be equally suitable to Australia C . salviniae for releases against giant salvinia , but further study is needed to fully assess the potential for using Florida C . salviniae against giant salvinia .
URI: http : / /hdl .handle .net /1969 .1 /3331
Date: 2006-04-12

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An evaluation of two strains of Cyrtobagous salviniae Calder and Sands as natural enemies of the aquatic weeds salvinia molesta Mitchell and Salvinia minima Baker. Available electronically from http : / /hdl .handle .net /1969 .1 /3331 .

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