Biological studies of Rhinocyllus conicus, Carduus thoermeri and a model of the interaction between these two species

A computer simulation model written in PL/I of the flowering phenology of C. thoermeri and the seasonal population dynamics of R. conicus was constructed based on a synthesis of the literature, and on laboratory experiments which determined developmental periods, mortality for immature stages and the ovipositional pattern of R. conicus. The model successfully simulated the ovipositional pattern of R. conicus and the flowering phenology of C. thoermeri. Larval population dynamics of R. conicus, in the model however, did not fit the validation data. Though the model was temporally synchronized with the field data, the model results were one degree of magnitude less. The poor fit was attributed to sampling errors in the validation data. Studies of the overwintering mortalities of both organisms were performed. R. conicus was found to overwinter with lowest mortality on musk thistle rosettes; mortality was 73.6% in 1981, higher than previously reported but possibly more representative of field conditions. No overwintering mortality was observed for established rosettes of C. thoermeri. Studies of seed dispersal of C. thoermeri were performed to determine the percentage of seeds removed from the vicinity of the plant where they originated. Seed dispersal observed for different wind velocities demonstrated that less than 1% of seeds are blown further than 100m and most seeds are deposited within 50m of the release site. A Gaussian model of seed dispersal based on experimentally determined parameters and literature values corroborated these results.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Entomology

Department dc:contributor.department

Entomology

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1982

Author dc:creator

• Smith, Lane Martin

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/76194

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/76194