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Predators play a critical role in regulating the structure and function of ecosystems by exhibiting top-down forces on lower trophic levels. Despite their important contributions in maintaining ecosystem health, lethal predator control remains a global wildlife management strategy to reduce predation on livestock, culturally and/or economically important species, and species at risk, as well as to reduce conflict with humans. Predator control has received criticism due in part to a paucity of rigorous research on the community-level impacts of this practice, beyond the target prey species. Specifically, there is a lack of understanding of the behavioural consequences of predator control on the wider ecological community. In this thesis, I used a multi-year camera trap dataset to evaluate how government-mandated grey wolf (Canis lupus) population reduction to conserve boreal woodland caribou (Rangifer tarandus caribou) could impact the resource selection of the carnivore community in northeast Alberta, Canada. In my second chapter, I investigated whether perceived persecution risk due to predator control may alter wolf habitat selection. I found that wolves switched from positively associating with roads before predator control to avoiding anthropogenic linear features and selecting for block features after predator control. These results suggest that lethal control may prompt wolves to prioritize local prey acquisition near block features over movement on linear features. In my third chapter, I examined whether coyote, lynx, and black bear exhibited shifts in co-occurrence with habitat features, competitors, and prey consistent with a release from top-down suppression in response to predator control. I found that predator control triggered unexpected behavioural changes among coyote and lynx consistent with a release from top-down suppression, but not among black bears. Non-apex predator response to predator control may depend on the strength of competition between the apex and non-apex predator, emphasizing the need to consider bottom-up processes when trying to understand the indirect effects of predator control. This research demonstrates that predator control can have trickle-down effects within the larger ecological community, specifically affecting how species utilize resources. As predator control continues to be a recommended wildlife management strategy, it is imperative to continue investigating its unintended consequences throughout the ecological community. / Graduate

<p>This study examined the self-trapping of light emitted by a miniature green laser in a photopolymerizable medium and the interactions between two parallel-propagating self-trapped beams. The work included the design and fabrication of an Intra-Cavity Frequency-Doubling (IC-FD) Nd: YVO₄/MgO: PPLN miniature green laser with a stable and tunable output intensity. Emission from this laser enabled a systematic examination of self-trapping phenomena at incident intensities spanning 8 orders of magnitude (3.2× W·cm^-2to 6368 W·cm^-2). When launched into a photopolymerizable medium, light emitted by the miniature green laser self-trapped by initiating polymerization and corresponding changes in refractive index along its propagation path. The evolution and dynamics of the self-trapped beam corresponded to the behaviour of self-trapped beams of coherent light. Interactions between a pair of parallel-propagating self-trapped beams were also characterised at a range of intensities. This study shows that the miniature green laser is an efficient, coherent source with a large range of output intensities for the excitation of self-trapped beams. This opens opportunities for its incorporation into small-scale optical systems designed to operate based on the generation and interactions of self-trapped beams.</p> / Master of Applied Science (MASc)

Harlequin bug (HB), Murgantia histrionica (Hahn), is a pest of cole crops. Alternative control strategies were investigated for control of HB, including trap cropping and systemic neonicotinoid insecticide applications. Potential trap crops, mustard (Brassica juncea "Southern Giant Curled" ), rapeseed (B. napus "Athena"), rapini (B. rapa) and arugula (Eruca sativa) were preferred over collard (B. oleracea "Champion"), and a non-brassica control, bean (Phaseolus vulgaris "Bronco") in field-cage choice tests. Harlequin bug could not complete development on bean, developed poorly on arugula but was found to complete development on mustard, collard, rapeseed and rapini. In the field, mustard was found to be an effective trap crop for reducing HB feeding injury on collard at three experimental sites in 2010 and 2011. Augmentation of the mustard trap crop with a systemic, neonicotinoid insecticide did not increase the level of control of harlequin bug for the duration of the ten week growing period. In olfactometer choice tests, male HB responded to plant volatiles of bean, collard and mustard, but preferred Brassica volatiles over those from bean. Female response to plant volatiles alone was weak and inconsistent. Both males and females preferred volatiles from other males feeding on Brassica host plant over plant volatiles alone, and were deterred by volatiles from males feeding on bean versus the plant alone. Laboratory toxicity assays revealed that the neonicotinoid insecticides imidacloprid, thiamethoxam, dinotefuran, and clothianidin were toxic to HB nymphs; LC50 = 0.57, 0.52, 0.39, and 0.39 mg ai/liter, respectively. Field experiments were conducted to evaluate the efficacy of these insecticides over time when applied as a one-time drench, and all were found to provide significantly higher mortality of HB for at least 14 days after application. / Ph. D.

Noninvasive methods for monitoring wildlife species have revolutionized the way population parameters, such as population density and survival and recruitment rates, are estimated while accounting for imperfect detection using capture-recapture models. Reliable estimates of these parameters are vital information required for making sound conservation decisions; however to date, noninvasive sampling methods have been of limited use for a vast number of species which are difficult to identify to the individual level–a general requirement of capture-recapture models. Capture-recapture models that utilize partial identity information have only recently been introduced and have not been extended to most types of noninvasive sampling scenarios in a manner that uses the spatial location where noninvasive samples were collected to further inform complete identity (i.e. spatial partial identity models). Herein, I extend the recently introduced spatial partial identity models to the noninvasive methods of remote cameras for species that are difficult to identify from photographs and DNA from hair or scat samples. The ability of these novel models to improve parameter estimation and extend study design options are investigated and the methods are made accessible to applied ecologists via statistical software. This research has the potential to greatly improve wildlife conservation decisions by improving our knowledge of parameters related to population structure and dynamics that inform those decisions. Unfortunately, many species of conservation concern (e.g., Florida panthers, Andean bears) are managed without having the necessary information on population status or trends, largely a result of the cost and difficulty of studying species in decline and because of the difficulty of applying statistical models to sparse data, which can produce imprecise and biased estimates of population parameters. By leveraging partial identity information in noninvasive samples, the models I developed will improve these parameter estimates and allow noninvasive methods to be used for more species, leading to more informed conservation decisions, and a more efficient allocation of conservation resources across species and populations. / Ph. D.

1.) Sentinel traps were used to survey for parasitoids of frugivorous drosophilids in Virginia fruit cropping systems, and determine if parasitoids were attacking invasive flies Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) in the field. Two parasitoids of frugivorous drosophilids, Leptopilina boulardi (Barbotin, Carton, and Kelner-Pillault) (Hymenoptera: Figitidae) and Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae), were reared, but only one P. vindemiae was reared from D. suzukii, and no parasitoids were reared from Z. indianus. Most parasitoids were reared from alternate host Drosophila melanogaster Meigen and other wild drosophilids. 2.) The ability of these parasitoids to attack D. melanogaster, D. suzukii and Z. indianus under controlled conditions was tested. Larval parasitoid L. boulardi did not develop on D. suzukii or Z. indianus, just D. melanogaster. Pupal parasitoid P. vindemiae successfully developed on all three fly species, but also increased pupal fly mortality. 3.) Olfactometry was used to ascertain if L. boulardi and P. vindemiae are selective about the type of fruit their hosts feed in. Results showed that among cherry, raspberry, blueberry, grape, and banana, L. boulardi preferred raspberry and banana to cherry, and preferred grape least, but no fruit was most preferred. Insufficient data were obtained for P. vindemiae. We conclude that parasitoids of Virginia are unlikely to provide effective biological control for D. suzukii or Z. indianus, and classical biological control should be investigated as a pest management option. Olfactometry results indicate tritrophic selectivity by Drosophila parasitoids, suggesting multiple parasitoids could be required for effective biological control. / Master of Science in Life Sciences

Pheromone lures and trap crops are appealing pest management tools that use insect and/or plant volatiles to reduce pest populations on crops of interest. Generating pheromone-emitting trap plants may allow for a continuing and highly-specific attraction of insect pests without repeated and costly application of synthetic pheromones. These trap plants may also be used to develop area-wide pest management strategies. As a proof-of-principle study we tested the possibility of producing the pheromone of the crucifer flea beetle Phyllotreta cruciferae in transgenic plants. P. cruciferae is an important pest of Brassica crops. In the presence of a host plant, males emit an aggregation pheromone, which attracts both males and females. Himachaladiene, a sesquiterpene, has been identified as a key component of the aggregation pheromone of P. cruciferae. In a close relative, Phyllotreta striolata, the compound is synthesized by a two-step pathway with an isoprenyl diphosphate synthase (PsIDS3) making (Z,E)-farnesyl diphosphate (FPP), which is converted by a terpene synthase (PsTPS1) to himachaladiene. Transient transformation of N. benthamiana with PsIDS3-TPS1 co-localized to the plastid resulted in the emission of himachaladiene and other known PsTPS1 products. Daily emissions of himachaladiene were approximately 1 µg per plant, which is six-fold higher than emissions from individual male flea beetles. Stable transformation of Arabidopsis thaliana with the same vector construct resulted in transgenic plants that expressed PsTPS1 and PsIDS3 transcripts, but no himachaladiene or other PsTPS1 products were present in volatile collections or leaf extracts of these plants. Moreover, no PsTPS1 enzyme activity was observed, indicating that post-transcriptional/translational effects prevent proper expression or targeting of functional PsIDS3 and/or PsTPS1 proteins in A. thaliana. Overall, this study demonstrates that the key component of the P. cruciferae aggregation pheromone, himachaladiene, can be transiently produced and emitted in a plant system at rates that are biologically relevant for insect attraction. However, further work is required for the stable production of the pheromone in plants. In addition, preliminary results are presented for the development of simple two-choice arenas that may allow for assessment of the movement of beetles toward host plant leaf tissue. This work can inform future efforts in developing methods for the economic production of himachaladiene in a plant system or the establishment of transgenic plants for the production and deployment of himachaladiene in a field setting. / Master of Science / The crucifer flea beetle is an important pest of vegetable and oilseed Brassica crops such as broccoli, cabbage and canola. Feeding by beetles has its greatest impact on crop health and yield in the early spring, when adult beetles emerge from overwintering sites and feed on newly- emerging Brassica seedlings. Currently these insects are controlled using broad spectrum insecticides. A general awareness of the negative aspects of insecticides drives the search for alternative pest management strategies that could diversify our management strategies and reduce reliance on insecticides. Previous work has found that the crucifer flea beetle navigates to its host plants, in part, through plant-emitted volatiles. After locating the plant host, males emit a volatile aggregation pheromone that when blended with host plant volatiles increases attraction. Here work towards the development of a specialized trap crop is presented. Plants were engineered to emit a key component of the crucifer flea beetle aggregation pheromone. In an engineered non-host plant, Nicotiana benthamiana, transient production of the aggregation pheromone was established. However, in an engineered Brassica plant, Arabidopsis thaliana, no aggregation pheromone was detected despite evidence of the presence and expression of the required biosynthetic genes for its production. A discussion on alternative engineering strategies for A. thaliana is presented. In addition, preliminary results are presented for the development of a simple behavior assay to assess the attraction of beetles toward different smells. This work can inform future efforts aimed at developing methods for the economic production of the aggregation pheromone in a plant system or the establishment of plants for the production and deployment of the aggregation pheromone in a field setting.

The planned widening of U.S. Highway 17 along the east boundary of Great Dismal Swamp National Wildlife Refuge (GDSNWR) and a lack of knowledge about the refuge's bear population created the need to identify potential sites for wildlife crossings and estimate the size of the refuge's bear population. I collected black bear hair in order to collect DNA samples to estimate population size, density, and sex ratio, and determine road crossing locations for black bears (Ursus americanus) in GDSNWR in southeastern Virginia and northeastern North Carolina. I also investigated bear/vehicle collisions to determine patterns of road crossing. Genetic analysis of 344 hair samples collected on 2 trapping grids identified 85 unique individuals which I used in a mark-recapture analysis. Estimated population size on the trapping grids was 105 bears (95% CI = 91-148) and average density was 0.56 bears/km². This density estimate projected over the entire Great Dismal Swamp ecosystem yielded a population estimate of 308 bears (550 km2 X 0.56 bears/km²). Similar population estimates generated by Hellgren (1988), Tredick (2005), and this study suggest a stable bear population in the Great Dismal Swamp ecosystem over a 20-year period. I erected a 2.3-kilometer long strand of barbed wire along U. S. Highway 17 to monitor road crossing patterns near the Northwest River drainage. Genetic analysis identified 6 bears (4 males, 1 female, 1 unknown) that apparently crossed the highway in a 10-month period. Five of 6 bears deposited hair in a 171-m section which included the Northwest River corridor. The 6 bears detected crossed the road at least 11 times. I investigated 10 reports of bear/vehicle collisions on the periphery of the refuge from June 2000 to May 2002. Six bears (4M:1F:1 unknown) were confirmed killed during this time period. Based on reported bear/vehicle collisions from Hellgren (1988), the Virginia Department of Game and Inland Fisheries database, and this study, a minimum of 4 to 5 bears are struck by vehicles each year on the periphery of the refuge. I identified 2 areas of multiple bear/vehicle collisions: highway 58 on the north side of the refuge near Hampton Airport and Highway 17 on the eastern side of the refuge in the vicinity of the Northwest River corridor. / Master of Science

Brown marmorated stink bug, Halyomorpha halys (Stål), is a crossover pest impacting agriculture and invading urban environments. Studies were conducted to better understand the management of the bug through its physiology, behavior and susceptibility to insecticidal intervention. Halyomopha halys exhibit great variability in overwintering site selection with choices including manmade structures and tree bark. Because of these diverse sites, the bug must have the ability to withstand varying conditions throughout the overwintering cycle. We were able to determine that H. halys is chill intolerant and capable of adapting its tolerance to temperatures by season, sex, and location of acclimation. The mean supercooling point (± SEM) in the winter in Minnesota was -17.06°C ± 0.13° and in Virginia was -13.90°C ± 0.09°. Laboratory experiments conducted in Blacksburg, VA were able to determine baseline lethal high temperatures over time against H. halys adults. To achieve 100% mortality, temperatures fell between 45°C and 50°C, 40°C and 45°C, and 42°C and 45°C, over 15-min, 1-h, and 4-h, respectively. Moving forward, we were able to utilize this information to develop heat treatment guidelines for export shipping cargo infested with overwintering H. halys. In a controlled field experiment, we determined that exposing the coldest areas of an infested vehicle to temperatures greater than 50°C for a minimum of 15 minutes resulted in 100% mortality of overwintering BMSB adults. In 2012 and 2013, citizen scientists were recruited through Virginia Cooperative Extension to assist in evaluating several in home light traps designed to help eradicate overwintering H. halys adults in homes. Over the course of the two year study, fourteen houses participated in the study with 72% of those houses having stink bug activity. It was found that the most effective trap was an aluminum foil pan trap. In 2013, the trap was 19 times more effective at catching stink bug adults than any other trap tested. In September of 2014, a near-field experiment was conducted to determine the residual efficacy of several recommended and labeled insecticides for treatment of homes against invading H. halys adults. This study used constructed window screen bags that were dipped in insecticide solution. After the initial treatment, bugs were exposed to the bags for 24h weekly, up to 54 days after treatment (DAT). It was determined that 2 DAT all insecticides had activity except for indoxacarb. All insecticides lost efficacy after 29 DAT except for lambda-cyhalothrin, beta-cyfluthrin, beta-cyfluthrin + imidacloprid, lambda-cyhalothrin + thiamethoxam, and dinotefuran, which had some measureable activity even after 40 DAT. Each of these insecticides contained a pyrethroid alone or in combination with a neonicotinoid. Laboratory bioassays were conducted to determine the LC50 values of clothianidin, dinotefuran, imidacloprid, and thiamethoxam against H. halys nymphs using a systemic application method. Those LC50 values were found to be 0.077, 0.013, 0.068, and 0.018 ppm, respectively. Field experiments conducted in Virginia in 2012 and 2013 showed a significant reduction of stink bug damage using two soil applications of neonicotinoid insecticides in pepper and tomato. In North Carolina, a single drip irrigation application significantly reduced stink bug damage in 2012 and 2014 using dinotefuran or imidacloprid. / Ph. D.