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 8.0ºC
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 26.5ºC temperature profiles. Neither strain reproduced, and no
significant between-strain differences in plant necrosis were detected at the 8.0ºC
temperature profile. At 31.4ºC there were no significant differences in adult counts,
larval counts or plant damage between the two strains on giant salvinia. At 26.5ºC,
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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3331 |
| Date | 12 April 2006 |
| Creators | Dye, Jeremiah M. |
| Contributors | Heinz, Kevin M., Jackman, John A. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 681211 bytes, electronic, application/pdf, born digital |
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