A three-year (1998-2000) field and laboratory study conducted in Fredericton, New Brunswick, Canada analyzed and quantified the dispersal of adult Colorado potato beetles within and between conventional and transgenic potato plots established according to the high-dose/refuge strategy. More specifically, the study addressed the following four predictions: (1) Adult Colorado potato beetle abundance or flight activity in transgenic potato fields is positively correlated to the abundance or flight activity in the immediately adjacent refuge field. (2) Colorado potato beetle intraspecific competition on potato plants will increase the flight take-off frequency of adult CPB; tolerating relatively high numbers of CPB egg masses or larvae or a high level of CPB defoliation on potato plants in the refuge could therefore be considered to increase the movement of beetles from the refuge to the transgenic field. (3) CPB flight take-off frequency will be higher on potato plants at the bloom than at the vegetative stage; planting of the non transgenic potato crop in the refuge earlier than the Bt transgenic potato crop in the main field could therefore be considered to increase movement of the Colorado potato beetles from the refuge to the transgenic field. (4) The aggregated distribution of CPB populations in the potato crop is caused by the presence of mating pairs; strategies changing the distribution of males and females in the refuge field could therefore be considered to increase dispersal from the refuge to the main crop field. / Population monitoring using plant counts, flight interception traps, flight landing traps and pitfall traps established that a transient population of adult CPB is present in the transgenic potato fields throughout the crop season and that the abundance of the beetle is higher than that required by the high dose/refuge strategy models. Furthermore results showed that the beetles invading the transgenic field population originate as much from the surrounding fields of conventional cultivars as from the adjacent refuges. It would therefore be possible to relax existing requirements for the refuge to be located immediately adjacent to the transgenic crop. / Like most insects, the adult CPB populations are aggregated and can be fitted to a negative binomial distribution over the crop season. This study revealed that the distribution results from the presence of mating pairs for the overwintered population and from the clumped pupation for the non breeding summer population. The activity of the males in search of females is at least partly responsible for the higher dispersal activity observed with the overwintered than with the summer populations. The comparatively low level of dispersal activity with the summer population could affect the efficacy of the high/dose refuge strategy during the later part of the crop season. / Results of flight chamber tests demonstrated that plant phenology and intraspecific competition have a positive effect on flight take-off frequency. These findings suggest that summer adult dispersal between the refuges and the transgenic crops could be stimulated by manipulating planting dates and the abundance of the different CPB life stages on the plants. / Together, the results of the thesis provide support for some of the premises of the high dose/refuge strategy and offer new information on the CPB dispersal that could be used to further improve its efficacy. Although the transgenic potato (NewLeaf) is not commercially available at this time, the threat of CPB resistance to new products or resistant cultivars under development makes it important to continue the research required by CPB resistance management plans.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102810 |
| Date | January 2006 |
| Creators | Mbungu, Nsitu T. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Natural Resource Sciences.) |
| Rights | © Nsitu T. Mbungu, 2006 |
| Relation | alephsysno: 002590008, proquestno: AAINR32215, Theses scanned by UMI/ProQuest. |
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