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Feeding and Oviposition Preferences of the Diamondback Moth Plutella Xylostella (Lepidoptera: Plutellidae) on Six Brassicaceae Host Plant Species

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Feeding and Oviposition Preferences of the Diamondback Moth Plutella Xylostella (Lepidoptera: Plutellidae) on Six Brassicaceae Host Plant Species View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Brock University Digital Repository Feeding and oviposition preferences of the diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) on six Brassicaceae host plant species By Kiera Newman, B.Sc. Submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Biological Sciences, Brock University St. Catharines, Ontario ©2014 Table of Contents List of figures .................................................................................................................... 3 List of tables ...................................................................................................................... 5 Abstract ............................................................................................................................. 6 Acknowledgements ……………………………………………………………………… 7 CHAPTER 1: Introduction………………………………………………………..…… 8 1.1 Insect Dispersal …………….…….…….….……………………………………. 8 1.2 Overcoming Plant Defenses ……………………………………….. …………… 10 1.3 Host Plant Preference……………………………………………………………. 12 1.4 Population Isolation and Gene Flow ………………………………………. …… 17 1.5 Study Species- DBM (Plutella xylostella)………………………………………. 19 1.6 DBM Life History…………….…………………………………………….…… 21 1.7 DBM Host Plant Preferences……….…………………………………………… 22 1.8 Proposed Study and Questions………………………………………………….. 26 CHAPTER 2: Are wild or ornamental plants more attractive than crops to Plutella xylostella larvae?………………………………………………………………………… 29 2.1 Abstract ............ .................................................................................................... 29 2.2 Introduction ........................................................................................................... 30 2.3 Materials and Methods ........................................................................................... 32 2.4 Results .................................................................................................................... 36 2.5 Discussion .............................................................................................................. 38 2.6 Figures…………………………………………………………………………….. 42 2.7 Tables……………………………………………………………………………… 44 CHAPTER 3: Diamondback moths find novel host plant attractive: preference of DBM (Plutella xylostella) for Lepidium sativum ........................................................................ 46 3.1 Abstract…................................................................................................................ 46 3.2 Introduction…………….. ....................................................................................... 46 3.3 Materials and Methods ............................................................................................ 50 3.4 Results......................................................................................................………… 52 3.5 Discussion ............................................................................................................... 53 3.6 Figures …………………………………………………………………………… 58 3.7 Tables…………………………………………………………………………….. 60 CHAPTER 4: Discussion and Conclusion……………………………………………. 62 4.1 Host Plant Preference and Fitness Consequences………………………………… 63 4.2 Population Differences……………………………………………………...……. 65 4.3 Instar Differences………………………………………………………..……….. 66 4.4 Conclusion and Future Research Directions ……………………………….……. 67 References………………………………………………………………………..………. 69 2 List of Figures 1.1 Insect establishment in a novel or seasonal environment begins with movement of individuals from a source population. Factors such as insect specialization, host plant nutrition, community dynamics of other species present, and plant defenses, all affect an insect’s ability preference for host plants and their ability to feed. Oviposition and subsequent development of young must also occur. Some insects have several generations per season. At season’s end, insects will die off, overwinter, or migrate back to their source population.………………………………………………………………………… 10 1.2 Predicted worldwide distribution of DBM (DBM) based on a validated bioclimatic model. Areas shaded in red show regions of the world where the Ecoclimatic Index (EI) is positive and DBM can persist year-round; red shading demarcates the core distribution of DBM (regions where EI ≤ 15–20 are marginal for year-round DBM survival). Areas shaded in blue show regions of the world where the EI is zero but where the annual growth index (GI) is positive; in these regions DBM cannot persist year-round but it can become a seasonal pest following influxes of moths from elsewhere (Furlong et al. 2013, with permission)…………………………………………………………………... 21 1.3 a. Window created in leaf by 2nd instar DBM larva b. 4th instar DBM larva feeding on a broccoli leaf c. Adult DBM beside its pupal case on an ornamental kale leaf d. DBM egg (source: Kiera Newman)………………………………. 23 1.4 Parasitoid (Diadegma sp.) of a DBM larva (source: Kiera Newman)…… 27 2.1 Number of DBM larvae (both 3rd and 4th instars combined) from all populations (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental) that chose each plant species or made no choice (n=191). Letters denote significant differences between plant species, as determined by Tukey post hoc tests.…………………………………………………………………… 43 2.2 Percent mean relative weight gain (RWG) of 3rd and 4th instar DBM larvae after one hour of feeding on different plant species (garden cress, wintercress, black mustard, aubretia, broccoli, and ornamental kale) (n=182) from all populations (Alberta, Saskatchewan, Ontario Crop, Ontario Wild, Ontario Ornamental) combined. Letters denote differences between plant species. Error bars represent one standard error above and below mean.……….......................... 44 44 3.1 Mean number of eggs oviposited per cm2 on various plant species by DBM females from five populations (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental) over four nights (n=240). Letters denote significant differences between plant species. Error bars represent one standard error above and below the mean………………………………………………….. 59 3.2 The mean numbers of DBM eggs oviposited on the upper and lower surfaces of each plant species (n=40) from all populations (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental) combined. Letters denote 3 significant differences. Error bars represent one standard error above and below the mean………………………………...………………………………………… 60 4 List of Tables 2.1 Summary statistics from a generalized linear model (GLZM) analysis of DBM plant species preferences (garden cress, wintercress, black mustard, aubretia, broccoli and ornamental kale) (as indicated through percentage of larvae that chose each plant type) between populations (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental), and larval instars (3rd and 4th). Significance levels were set to α=0.05; < 0.05*, <0.01**, <0.001***……….…… 45 2.2 ANOVA summary statistics for DBM weight gain over one hour of feeding by all larvae (n=182) on six different Brassicaceae plant species (garden cress, wintercress, black mustard, aubretia, broccoli and ornamental kale) and from five different populations (Alberta, Saskatchewan, Ontario Crop, Ontario Wild, Ontario Ornamental). Significance levels were set to α=0.05; < 0.05*, <0.01**, <0.001***………………………………………………………………………….. 45 2.3 ANOVA results for DBM weight gain over one hour of feeding on six different Brassiceae plant species (garden cress, wintercress, black mustard, aubretia, broccoli and ornamental kale) in 3rd (n=94) and 4th (n=97) instar larvae for all populations combined (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental). Significance levels were set to α=0.025; < 0.025*, <0.001**, <0.001***………………………………………………………………. 46 3. 1 Generalized linear model (GLZM) summary statistics for the number of eggs laid on each of six different plant species (garden cress, wintercress, black mustard, aubretia, broccoli and ornamental kale) by DBM females from five populations (Alberta, Saskatchewan, Ontario Crop, Ontario Ornamental, Ontario Wild) combined. Significance levels were set to α<0.05*, <0.01**, and <0.001***………………………………………………………………………… 61 3.2 The average number of eggs (on upper and lower leaf surfaces together) oviposited by DBM adult females (n=40) on each plant species (garden cress, wintercress, black mustard, aubretia, broccoli and ornamental kale) for all populations combined (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental). Mean eggs per plant and mean eggs per cm2 are shown…... 61 3.3 Chi-square test summary statistics for DBM eggs laid on upper and lower surfaces of all plant species together (garden cress, wintercress, black mustard, aubretia, broccoli and ornamental kale) for all populations combined (Alberta, Saskatchewan, Ontario Crop, Ontario Wild and Ontario Ornamental). Significance levels were set to α<0.05*, <0.01**, and <0.001***………………... 62 5 Abstract Plutella xylostella (diamondback moth, DBM) is a globally distributed Lepidopteran that feeds and oviposits almost exclusively on plants in the Brassicaceae family. DBM disperses from the southern United States and Mexico into Canada in the spring and summer. Establishment of DBM in Ontario is partially dependent upon the quantity and quality of host plants available and the preference of DBM for different hosts. Host plants include many crops
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