Following the plume: Development of a pheromone-based monitoring and management program for Coleophora deauratella (Lepidoptera: Coleophoridae)

• Author / Creator

  Mori, Boyd AR

• The reliance of moths on pheromone-mediated communication for mate location makes sex pheromones ideal candidates for exploitation in integrated pest management (IPM) programs. Pheromones make sensitive tools that can detect invasive species at low population densities and in new habitats. The red clover casebearer, Coleophora deauratella Leinig and Zeller (Lepidoptera: Coleophoridae), is an invasive pest of clover throughout North America. In Canada, infestations of C. deauratella in red clover seed production fields can cause > 80% seed loss and insecticides have been ineffective against this pest. Recently, the sex pheromone produced by C. deauratella females was identified as a 10:1 ratio of (Z)-7-dodecenyl acetate and (Z)-5-dodecenyl acetate. This identification allows synthetic pheromones to be used for detection and management of this invasive pest. In this thesis, I investigated several non-pheromone factors that can influence the efficacy of pheromone-baited traps. I found that green unitraps placed 35 cm above the soil surface and 5 m from the field edge maximized capture of C. deauratella and minimized by-catch of non-target organisms. I then used this optimized trapping system to develop a pheromone-based monitoring program that can monitor male C. deauratella population density and flight phenology. Male C. deauratella captures were significantly and positively related to larval abundance and proportion of seed damage even with moderate to high population densities. A phenological model based on degree days (base 11.7 °C) more consistently described the median flight period of male C. deauratella compared to the ordinal date model. Further, the model found that 258.3 DD11.7 from January 1 are needed for median flight to occur. In addition, I tested pheromone-mediated mating disruption formulations to determine if treatment interferes with mate finding, reduces larval abundance, and increases seed yield. Results from small-plot (0.25 ha) field experiments with rope, aerosol-emitter, and laminate-flake pheromone dispensers demonstrated male C. deauratella orientation to pheromone-baited traps was reduced 60-99% in treated compared to non-treated control plots. In large-plot (5 ha) experiments, aerosol-emitting pheromone dispensers reduced male C. deauratella orientation to pheromone-baited traps, but no reduction in larval numbers or increase in seed yield was found compared to untreated control plots. However, a significant reduction in C. deauratella captures in pheromone-baited traps and larval numbers and an increase in seed yield were observed using laminate flakes. I also investigated the mechanisms through which pheromone treatment acts to disrupt mating by C. deauratella. Complete and partial pheromone formulations were compared to determine the capacity and mechanisms of both formulations to cause disruption. The partial pheromone formulation was as successful as the complete pheromone blend for reducing male C. deauratella orientation to pheromone-baited traps. Small-plot field trials, combined with laboratory electroantennograms, determined that both competitive and non-competitive mechanisms may cause mating disruption when the complete pheromone blend is used, whereas non-competitive mechanisms were primarily invoked with the partial formulation. Additionally, studies on laminate flake dispensers found theoretical models of competitive attraction to be supported. In order to identify the source of C. deauratella populations and determine possible routes of invasions in North America, I used pheromone-baited traps to collect specimens throughout North America and Europe. I isolated and characterized four polymorphic microsatellite loci for C. deauratella and combined their use with mitochondrial DNA to examine genetic diversity and population differentiation. Most genetic differentiation was observed between continents; little differentiation and no evidence of isolation-by-distance were found between populations within each continent, suggesting C. deauratella has been readily transported across large distances. The low number of haplotypes observed in North America, combined with clustering analyses suggest only two genetic clusters are present, and indicate that a limited number of invasion events occurred in North America. The initial C. deauratella invasion most likely occurred in southern Ontario or adjacent American states followed by subsequent transport throughout the continent, however, the precise source population could not be inferred by this study. Ultimately, these investigations could form the basis of a comprehensive IPM program that can detect, monitor and manage this pest throughout North America. Mating disruption will provide growers with a non-insecticidal control option to help mitigate damage caused by C. deauratella. Furthermore, determination of the origins of C. deauratella in North America may help focus the search for biocontrol agents to control the introduced populations.

• Subjects / Keywords

  • Lepidoptera
  • Pheromone
  • Coleophora
  • Pheromone monitoring
  • Mating disruption
  • Microsatellites

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3DB7VZ4H

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.