Ph.D. - Entomology

Permanent URI for this collectionhttps://hdl.handle.net/10125/1834

Browse

Now showing 1 - 20 of 56

Efforts to Slow the Spread of Invasive Species in Hawai‘i: A Focus on Integrated Pest Management Strategies for the Coconut Rhinoceros Beetle, Oryctes rhinoceros and the Hala Scale, Thysanococcus pandani
(University of Hawai'i at Manoa, 2024) Russo, Mason Harry; Wright, Mark G.; Entomology
The Hawaiian islands have been subject to a series of invasive plant, insect, vertebrate, and pathogen introductions. This started with the first Polynesian arrivals, increased with European contact, and substantially increased as globalization ensued. These introductions have resulted in the extinction of many endemic species and have altered many ecosystems from dryland forests to high elevation areas. This dissertation will focus on two specific invasive insects, the coconut rhinoceros beetle, Oryctes rhinoceros Linnaeus and the hala scale, Thysanococcus pandani Stickney. These insects impact native species and have caused ecological, cultural, and economic damage.Oryctes rhinoceros is an invasive insect that feeds primarily on coconut palms. It was previously controlled with the release of specimens infected with the virus, Oryctes rhinoceros nudivirus (OrNV, Alphanudivirus oryrhinocerotis). However, beetles resilient to OrNV were found in Guam, where they became widespread. Since then, this biotype of O. rhinoceros was found on the Hawaiian island of O‘ahu in 2013. This triggered an extensive eradication program using tools such as mass trapping, detector dogs, green waste sanitation, and insecticidal treatments. Populations have since spread across O‘ahu, and in 2023 highly localized O. rhinoceros populations were found on Maui, Kaua‘i, and Hawai‘i island. The insecticidal studies evaluated the efficacy of systemic insecticides in laboratory and field settings as a potential component of the long-term integrated pest management program for O. rhinoceros. The laboratory assays tested the efficacy of imidacloprid, dinotefuran, and abamectin at 25 and 250 parts per million (ppm) on adult O. rhinoceros beetles. Two concurrent field trials were conducted to evaluate the preventative and curative effects of injecting imidacloprid, dinotefuran, abamectin, and acephate into coconut palms trunks. Efficacy of treatments was determined by taking monthly visual measurements of O. rhinoceros feeding damage. Palm fronds were removed and tested on laboratory-starved beetles to see if feeding exposure caused negative impacts. The results of the laboratory trials indicated that all the chemicals were effective at both 25 and 250 ppm and that pesticide residue in palm fronds caused negative impacts as late as seven months after treatment. The field trial results indicated that imidacloprid injections reduced the total amount of new feeding damage, with chemical residue remaining seven months post treatment in palms. I conducted an areawide injection trial at this site that had inconclusive results. I conducted further trials to evaluate commercial and locally occurring entomopathogenic fungi that could be implemented to mitigate O. rhinoceros populations. I also conducted trials with locally collected entomopathogenic nematodes that did not yield significant mortality. Our initial laboratory trials in 2018 and 2019 narrowed down five locally collected fungal strains with greater than 60% mortality rates on first instar larvae. In 2021 these strains were tested in conjunction with the fungal insecticide BotaniGard ES, with decreased efficacy in some strains, but greater than 60% mortality with BotaniGard ES at the high label rate. In field trials there was greater than 60% mortality of first instar larvae using BotaniGard ES as a mulch amendment. This treatment is unfortunately difficult to implement in the field due to the shelf life of the product. The studies pertaining to T. pandani covered a variety of knowledge gaps surrounding this rarely studied insect. In Hawai‘i it was first detected in Hāna, Maui in 1995, and its primary host plant is the indigenous hala tree, Pandanus tectorius, which is found in coastal and riparian areas throughout the Hawaiian islands. It has been found on Moloka‘i, O‘ahu, Lāna‘i, and Hawai‘i island, but T. pandani is only widespread on the islands of Maui and Moloka‘i. The insect is a sedentary feeder on the leaves and fruit, and heavy infestations result in discoloration, frond, and possible tree death. Experimental field trials were set up to evaluate the efficacy of organic and chemical insecticides as potential treatments to mitigate the damage of T. pandani infestations. This was done on the Island of Maui where T. pandani is widespread. These trees were inoculated with T. pandani and evaluated throughout the trials for changes in plant height, canopy width, scale mortality, and visual infestation ratings. The results of two repeated field trials indicated that flupyradifurone and buprofezin were effective treatments in reducing the hala scale infestation and improving visual aspects related to plant health. In 2021 and 2023, statewide surveys were conducted to evaluate the distribution of T. pandani, and a dispersal study was set up on Maui in January 2023 to determine the ability of T. pandani to spread from infected to healthy hala trees over time. The visual surveys involved evaluating hala trees throughout plant nurseries, landscaping plantings, urban and residential areas, and forests. The dispersal study evaluated factors such as wind, spatial separation, population levels, and infestation ratings. The visual survey results indicated T. pandani is widespread on Moloka‘i and Maui, with established populations on O’ahu. The infestations on Lāna‘i and Hawai’i island were successfully eradicated. The dispersal study indicated that T. pandani was able to infest the entire field plot in the first 10 months. Available literature indicates that T. pandani infestations prevent seedling regrowth, suggesting that the hala forests on Maui and Moloka‘i may not regenerate. I carried out a statewide population structure study of coastal P. tectorius forests to test if presence of the hala scale was correlated with lower levels of recruitment. In 93 transects across four islands, this study documented population structure, hala scale presence, and biotic and abiotic factors that may also affect regeneration, including elevation, canopy openness, and understory invasive species cover. Heavy infestations of T. pandani infestation were present in all transects across forests on Maui and Moloka‘i, while Kaua‘i and Hawai‘i island did not have any infestations. Canopy cover varied across sites and relatively low levels of invasive plant cover were found in the understory. There was significantly lower sapling recruitment ratio (saplings (1-2m tall)/adult tree) within transects with the hala scale than those without. However, this result was driven by a single outlier. Immediate regeneration of P. tectorius may be inhibited by non-native plants and ungulate feeding. We conducted biological control surveys in Thailand, Indonesia, and Singapore to search for insects that could control T. pandani. The first trip found generalist coccinellidae predators and a botanical collection where it was found had many Pandanus spp. from Madagascar. In a survey to Madagascar, I found three undescribed scale species on various pandanus species, but no immediate evidence of T. pandani or biological control. The results of these studies helped fill knowledge gaps pertaining to integrated pest management of O. rhinoceros and T. pandani. I was able to conduct a variety of ecological and applied studies for T. pandani. These pests can severely alter the aesthetic landscape in urban areas of Hawai‘i that are characterized by palm and Pandanus plantings. They also have the ability to negatively impact natural areas with endemic Pritchardia spp. palms and wide ranging Pandanus forests found on coastal areas along the Hawaiian islands. It is possible that the spread of these pests within islands was facilitated by widespread urban planting of these species, thus creating a pathway for widespread dispersal of these pests throughout each island. In general, the accidental transport of these pests results in a range expansion within an island, or to a new area in the state. Public outreach and improved biosecurity protocols can mitigate the impacts of these pests. As these insects are not yet widespread across every Hawaiian island, further research and mitigative measures are necessary to slow the momentum behind the invasion of these pests.
BIOLOGY, ECOLOGY, AND MANAGEMENT OF PROSAPIA BICINCTA (HEMIPTERA: CERCOPIDAE) IN HAWAIʻI RANGELANDS
(University of Hawai'i at Manoa, 2024) Wilson, Shannon; Wright, Mark G.; Entomology
Human mediated activities have resulted in the introduction of thousands of non-native organisms to the Hawaiian Islands, making this archipelago a hot spot for invasive species. Invasive species threaten the persistence of Hawaiʻi’s unique and diverse endemic species and native ecosystems and impact the state economy, local agriculture, water quality, nutrient cycling, culture, and human health. Substantial efforts have been devoted to the research, development, and implementation of invasive species management plans in Hawaiʻi to mitigate the detrimental impacts, conserve biodiversity and endemic species, and protect the limited agricultural resources. However, invasive species management continues to be a significant challenge across the islands. Spittlebugs (Hemiptera: Cercopoidea) are not native to Hawaiʻi, but three species have been unintentionally introduced. The twolined spittlebug, Prosapia bicincta, is the first of species in the family Cercopidae to invade Hawaiʻi. Since its initial detection in 2016, it has become a highly invasive and destructive forage grass pest, damaging thousands of hectares of pastures and threatening the persistence of the economically, ecologically, and culturally significant beef cattle industry in Hawaiʻi. In this study, I investigated the biology, ecology, and impacts of P. bicincta in Hawaiʻi rangelands by quantifying the geographic distribution and seasonal abundance, determining environmental factors influencing population dynamics, assessing spatiotemporal changes in the dynamics of rangeland plant communities, and investigating food plant associations. Five years of monthly field surveys in the Kona district of west Hawaiʻi island revealed season (wet vs. dry) and elevation were the most significant factors indicative of P. bicincta distribution and seasonal abundance patterns. Monitoring from 519 to 1,874 m above sea level (a.s.l.) indicated pastures located between 1,000 to 1,300 m a.s.l. had the highest abundance of P. bicincta and experienced the greatest decrease in grass cover. Prosapia bicincta modified rangeland plant communities by causing severe grass dieback of key forage grasses and facilitating the establishment of weedy forbs and shrubs. This pasture pest was most abundant between April-October when rainfall was highest in Kona. Majority of the food plant associations were grasses, but there were also detections on legumes, sedges, and forbs. These findings on the distribution and abundance of P. bicincta in Kona provide information on the seasonality and life cycle duration under local conditions which will improve the effectiveness of management by indicating when control tactics should be implemented to target vulnerable life stages (i.e., nymphs and eggs). Monitoring of seasonal pest abundance supports management decisions as it provides a measure of the severity of infestation and if management costs are justified, allows for early detection in new areas, helps predict areas at high-risk of invasion, and can be used to gauge the efficacy of management actions. Furthermore, I evaluated forage grass susceptibility to adult feeding to initiate research on the development of host plant resistance as management strategy for P. bicincta since it is one of the most suitable tools for spittlebug control in extensive pasture systems. Results indicated the incorporation of resistant grasses is a promising management strategy against this pest as multiple grass species and cultivars exhibited high levels of resistance in terms of foliar damage, above- and below-ground dry biomass, and estimated functional plant losses. Seven grass species and cultivars incurred little to no foliar damage during and after adult infestation in the greenhouse. Among these, six species/cultivars showed no significant difference in dry mass between infested and control plants, and five had considerably low functional plant losses. In contrast, Kikuyu grass, Hawaiʻi’s most widespread forage, was extremely susceptible and presented high levels of foliar damage, showed significant reductions in above- and below-ground dry biomass, and sustained the greatest amount of functional plant losses. These findings suggest Kikuyu grass pastures infested with economically important levels of P. bicincta will warrant replacement with more resistant forages such as those observed in this study. Confirmation of forage resistance to P. bicincta adults provides a foundation for developing and implementing host plant resistance as a management tactic. Additionally, a follow up study was initiated to investigate if the resistance observed in the greenhouse was also observed in the field and assess grass ability to establish across the highly variable growing conditions in Kona pastures. However, manual establishment of nine field plots (each containing 32 subplots of eight grass species/cultivars) distributed across three ranches proved to be extremely labor intensive and took significantly longer than anticipated, ultimately delaying data collection. Preliminary data based on six monthly surveys indicated the five most resistant varieties in the greenhouse only accounted for <10% of the total nymphs detected in the field plots. Lastly, I assessed the response of Kikuyu grass to increasing densities of P. bicincta by quantifying the foliar damage presented during and after infestation and comparing above- and below-ground dry biomass of infested and control plants. Results indicated 75 adults/m2 was a catastrophic threshold for Kikuyu grass and above- and below-ground dry biomass of Kikuyu infested with ≥108 adults/m2 differed significantly from the dry mass of control plants. These results have major implications for Hawaiʻi rangelands as it provides a reference value for estimating an action threshold for the most dominant forage grass. The action threshold indicates when management should be implemented to reduce P. bicincta populations before the level of 75 adults/m2 reached. This ensures the costs of management actions are justified based on the pest density and helps prevent the economic injury level from being reached. The findings presented in this dissertation demonstrate the impact of insect pests on forage crops and the dynamics of rangeland plant communities over time and space, highlight the major factors driving insect pest distribution and abundance, underscore the effects of different ecological conditions on the biology of an invasive species, and provide a foundation for management of a highly invasive pasture pest. These findings improve our understanding of insect pest biology, ecology, distribution, seasonal abundance, and impacts on plant communities beyond the native range, thus, highlighting the variation in pest impact, life cycle, and habitat associations across different regions. Ultimately, the knowledge gained from this work contributes to the development and implementation of pest management strategies in pastures.
Parasitoids of invasive Scolytinae in Hawaiʻi, their biology, and potential for biological control
(University of Hawai'i at Manoa, 2024) Honsberger, David; Wright, Mark G.; Entomology
These studies explore the diversity and biology of parasitoids of Scolytinae and other wood boring beetles in Hawaiʻi, and attempt to determine the potential of some of the species for biological control of invasive pests of agriculture and forests. Associations between parasitoids and hosts that develop within or on the surface of wood and other plant parts were elucidated through collection and dissection of the plant parts, isolating and identifying parasitized hosts. Eight of the ten parasitoids of Scolytinae found in these studies were unrecorded, likely undescribed, and had unknown biology. Given that arthropod biodiversity in Hawaiʻi is more studied than in many world regions, it appears that much diversity, especially of cryptoparasitoids of wood boring insects, is yet to be found, both in Hawaiʻi and worldwide. Because of their highly concealed life history, most parasitoid-host association records for Scolytinae have historically been determined from patterns of emergence. A study of insect emergence from recently cut logs repeated over approximately a year allowed testing of the reliability of patterns of emergence in determining associations. Analysis of correlation of numbers of parasitoids and hosts emerging, relative timing of peak emergence of parasitoids and hosts, and distributional similarity in patterns of emergence of parasitoids and hosts showed that emergence patterns are unreliable predictors at least in the systems studied, largely producing false positives and leaving many true associations undetected. Therefore in all but the most obvious circumstances, patterns in emergence do not substitute for direct observation in determination of parasitoid-host associations for wood-associated insects. The biology of some of the new species of parasitoids of Scolytinae is described. Phymastichus holoholo sp. nov., along with Phymastichus xylebori (Hymenoptera: Eulophidae), are parasitoids of the adult stage of Xyleborus beetles. High percent parasitism is found in some habitats, and P. holoholo was also found parasitizing Euwallacea fornicatus and Euwallacea perbrevis inhabiting the same wood, though this appears rare. Acerocephala hanuuanamu sp. nov. is a cryptoparasitoid of Cryphalus spp. in the phloem layer under bark. Observed using phloem-sandwich observation chambers, it creates a tube through which it feeds and oviposits through the hard pupal chamber constructed by its host. The genus Acerocephala is revised and redescribed given two new species found and their functional morphology. Two Prorops spp. are found to be ectoparasitoids of adult Hypothenemus eruditus, one of these also occasionally encountered on other Hypothenemus spp., notably H. seriatus in macadamia husks. The nose-like projection characteristic of the genus was observed to function as a tongue and groove mechanism to hold open the membraneous region between the pro- and mesothorax of the host, exposing this soft spot on the beetle to use for host feeding and oviposition. Observation that A. hanuuanamu will readily parasitize and develop on Hypothenemus hampei larvae when placed into the tunnel systems of its usual hosts, but lack of ostensible interest in coffee berries, suggests the possibility of attempting to condition these parasitoids to take more interest in the coffee-CBB system. An experiment was performed placing A. hanuuanamu pupae into the host-habitat of CBB, so that adults would emerge into that environment, and subsequently tested their interest in CBB-infested coffee berry olfactory cues in an olfactometer. A significant increase in attraction to CBB-coffee in wasps emerged into this environment was not detected, but they were found to be less repelled to infested coffee relative to wasps that emerged into an environment resembling that of their usual hosts. This result is discussed in a general sense regarding conditioning of parasitoids, and for its implications about any possible utility of conditioning these parasitoids for use in drying parchment or coffee fields. The two Phymastichus spp. parasitize three of the five beetles known to be involved in spread of Rapid ʻŌhiʻa Death, a fungal disease killing ʻōhiʻa lehua trees, the major component of many forest types in Hawaiʻi. Host-habitat searching cues and host acceptance cues of P. holoholo were studied in an attempt to utilize this species against the disease vectors. Such cues were also explored to better understand searching and host acceptance behavior in parasitoids of Scolytinae; current knowlege regards only a few conifer-associated species. Parasitism was not found in beetles in ʻōhiʻa trees, though was prevalent in macadamia groves near the areas searched, and it was unclear if this was because the parasitoids are unable to parasitize the beetles in ʻōhiʻa, or because they are not attracted to the tree-beetle interaction in ʻōhiʻa. If the latter is true, an attractant could potentially be used to increase parasitism in susceptible trees. Using visually identical bolt-shaped traps containing different olfactory treatments, wood naturally colonized by insects including Scolytinae was found to be much more attractive than wood of otherwise similar condition without insects, or empty traps. Taking frass of a host as the putative cue mediating this interaction, a GC-MS analysis was performed, biologically promising volatile compounds identified, and a volatile blend was constructed and tested as an attractant. Experiments did not find an effect of the volatile blend alone, but it appeared to act synergistically with early-stage decaying wood to attract the parasitoids over wood alone. The attractant effect, though, appears too weak to be useful in biocontrol strategies that aim to attract parasitoids to a specific habitat or substrate. Though a successful attractant was not found, and the hosts and parasitoids were unable to be captively reared in these studies, shortcomings of these experiments are discussed; lack of success here does not mean this cannot be achieved. Predicated on rectifying these issues in further studies, ideas regarding biocontrol strategies for the ROD-associated Xyleborus beetles are discussed.
Seasonal Honey Bee Colony Performance and Health in Hawai'i
(University of Hawaii at Manoa, 2022) zhang, zhening; Wright, Mark G.; Entomology
The European honey bee (Apis mellifera) is among the most abundant pollinator species and the most widely managed insect in the world. In temperate areas, honey bee colonies experience large fluctuations in population throughout a year without becoming completely dormant. Numerous studies conducted in temperate regions focus on those seasonal changes and examine colony performance and overall health; however, there is little known about colony dynamics in Hawaii, where in spite of more stable ambient temperature and less pronounced seasons, there are notable changes in colony strength across the year. Hawaii does not have extremes of cold winters and hot summers, and the average daily temperature variation is small (around 3 ℃). Hawaii however, has large variations in rainfall patterns both at the regional level, especially when windward and leeward areas are compared, but precipitation also varies throughout the year. The subtropical climate of the islands is part of what makes year-round beekeeping possible in Hawaii. The Hawaiian islands are also a unique place to conduct research because the bees are 100% pure European stock, with no hybridization with African bees, as is the case in the southern U.S.The overall objective of this dissertation is to describe the seasonal growth patterns of honey bee colonies and examine possible health fluctuations under Hawaii’s climate. The results from this work contribute to basic knowledge for beekeepers, not only in Hawaii but also in other tropical areas with similar climates. Four objectives are covered in this dissertation. First, this work examines how foraging activities change across different parts of the year and how queen replacement events impact foraging. The data confirm that there were seasonal trends in colony growth in Hawaii and that the growth pattern could also be different between years, possibly due to the El Niño and La Niña phenomena. The climate in Hawaii allows for colonies to attempt queen replacement, whether it is through swarming or supersedure, during the majority of months of the year. Both swarming and supersedure led to a decreased exiting foragers per minute (EF). In contrast, the proportion of pollen foragers (P%) increased after supersedure but dropped after swarming. The degree of change in EF and P% during a swarming or supersedure event were found to be linked to its initial EF and P% before the queen replacement happened. Second, a supplemental feeding experiment was conducted for the first time in Hawaii to examine the potential benefits to colonies and local beekeepers. The results showed that colonies that received supplemental food began to grow larger than control colonies by the end of the feeding period. Most interestingly, the colony strength and larger population benefits dervided from feeding carried over to the post-feeding period. Colonies that were being fed produced nearly twice as much honey compared to the control group at the end of the study. In addition, control colonies showed a higher deformed wing virus level than the fed group. Third, climate data were used to make connections with seasonal colony growth. The analysis showed that besides temperature, daylight duration was the main trigger that impacted the colony's seasonal growth in Hawaii. Fourth, two master DWV variants, A and B, were examined at both colony and apiary levels across different months in 2018 and 2019. This study showed the prevalence of DWV-B had increased since the 2016 study. DWV-A was still dominant at an apiary level in this study; however, some colonies could already be characterized as DWV A+B mix or even DWV-B only. And finally, this study showed DWV-B had a seasonal change in both viral load and prevalence, providing a perspective on the dynamic nature of DWV master variants. Overall, the findings in this dissertation help to better understand the seasonal activity and health of honey bee colonies in a sub-tropical environment. This work provides valuable data to beekeepers in Hawaii and will contribute to the improvement of the overall colony conditions in Hawaii, both from a biological and economic perspective. The emerging of DWV-B in this study apiary also showed that there are rapid evolutionary changes between the varroa mite, the honey bee, and the DWV compared to the other parts of the world.
Investigating Patterns And Variations In Aedes Albopictus (Diptera: Culicidae) And Its Microbiome In Hawaii
(University of Hawaii at Manoa, 2021) Seabourn, Priscilla Sheryl; Medeiros, Matthew CI; Spafford, Helen; Entomology
Understanding the drivers of distribution and abundance of invasive species remains a significant challenge especially on the Hawaiian Islands. Mosquitoes (Diptera: Culicidae) are non-native to Hawai’i and the diseases they vector are a contemporary threat to human and wildlife health. Despite being a well-established mosquito species, Aedes albopictus (Skuse) distribution and the factors influencing the population and its host associated microbiome in Hawaiʻi are poorly understood. In this study, I investigate how the environment influences the distribution and abundance of Ae. albopictus and the diversity and distribution of its host-associated microbiome in Hawaiʻi. In a yearlong island-wide surveillance study on Maui, the patterns of mosquito distribution were evaluated in relation to environmental factors (rainfall and temperature), elevation, space, and time using both oviposition and adult traps. Overall, four mosquito species were detected, Ae. albopictus, Ae. vexans, Culex quinquefasciatus, and Wyeomyia mitchellii. The survey determined that Aedes albopictus is abundant and widely distributed around Maui, and adult abundance and oviposition varied with site and time of collection. The oviposition of Ae. albopictus was positively associated with sites that are warm and low elevation, while the abundance of adults was not influenced by the environmental variables. The complex characteristics of each site such as vegetation, land use and host availability likely influenced the abundance of adult Ae albopictus and its ovipositional activity. However, Culex quinquefasciatus, Ae. vexans, and W. mitchellii were not frequently collected, and were not assessed in relation to space, time, or environmental variables. The trapping methods and frequency and intensity of sampling are likely to have been the main drivers behind the probability that these species and others were collected. Nonetheless, these findings can be used provide a baseline for future mosquito surveillance studies to assess new mosquito species incursions, and range expansion. Adult Ae. albopictus collected in the above survey were used to assess host associated microbiome in relation to space, time, rainfall, temperature, and host infection with a co-occurring pathosymbiont Ascogregarina taiwanensis. The microbiome of Ae. albopictus was found to vary across the island and be influenced by infection status with A. taiwanensis. The microbiome of Ae. albopictus did not shift in accordance with gradients of temperature or rainfall, suggesting that mosquitoes actively maintain their microbiome. As with the distribution of the adult mosquitoes, the complex factors associated with various sites, are diving the differences in the host-associated microbiome across geographic location. This study also highlights that inter- and intra-domain interactions may structure the Ae. albopictus microbiome. Cumulatively, understanding the explicit drivers of the mosquito microbiome assembly may have important implications in developing mosquito control strategies. I further explored how the microbiome is heterogeneous within the host and demonstrate that the environment provides the source of microbes. Results indicate that the microbiome of Ae. albopictus tissues is compositionally nested within the environmental microbiome i.e. microbes within the mosquito tissues are also found in the soil, water and on plants in the mosquito habitat. Within the mosquito, the microbiomes of the crop, midgut, Malpighian tubules, and ovaries differed in composition. The microbiomes of mosquitoes tissues formed two specialized modules, one in the crop and midgut and another in the Malpighian tubules and ovaries. The specialized modules may form based on microbe niche preferences and/or selection of mosquito tissues on specific microbes that may aid unique biological functions of the tissue types. Strong niche-driven assembly of tissue-specific microbiotas from the environmental species pool suggests that each tissue has specialized associations with microbes, which perhaps derive from host-mediated microbe selection. Overall, this study investigated the drivers of distribution, and abundance of Ae. albopictus and additionally the diversity, distribution and abundance of the host-associated microbiome present in Hawaii. These findings fill an important gap in understanding about a significant disease vector and provide information for future surveillance and studies, particularly those that lead to the development of novel methods of mosquito management.
Chiggers (Acari: Trombiculidae) infesting Papua New Guinea land mammals
(University of Hawaii at Manoa, 1977) Goff, M. Lee; Entomology
Examination of over 10,800 specimens of chiggers from the island of New Guinea has revealed the presence of 45 species in 11 genera infesting 53 kinds of mammal hosts. One of these species was in the subfamily Leeuwenhoekiinae and the remainder in the Tro
Enhancing Male Annihilation Technique (MAT) of Fruit Flies (Diptera: Tephritidae) Using a Binary Lure System with a Biopesticide
(University of Hawaii at Manoa, 2020) Souder, Steven Kazunori; Spafford, Helen; Entomology
The family Tephritidae encompasses more than 4400 species worldwide from 500 genera. This family is one of the largest in the order Diptera that includes over 200 species of economic importance (Christenson & Foote 1960, White & Elson-Harris 1992). Economically important fruit flies can be serious pests of fruits, nuts, and vegetables that create adverse social, political, and economic hardship around the globe (Papadopoulos 2014). Extensive research and regulatory resources have been put towards pestiferous flies to reduce established populations, prevent transfer to fruit fly free areas, and effect quarantines and eradications (Vargas et al 2014). One technique used to combat these invasive pests is the use of the male annihilation technique (MAT; a.k.a. male attractant treatment). Male annihilation technique is the deployment of a high density of traps or bait stations that consists of an attractant combined with an insecticide and matrix. Where more than one species of fruit flies attacks a single crop, management becomes even more difficult and further research is needed. Papaya (Carica papaya L.) is a specialty crop that is of significant importance to Hawaiʻi’s diversified agriculture. In Hawaiʻi, papaya is attacked by both Bactrocera dorsalis (Hendel, est. 1945) and melon fly, Bactrocera (Zeugodacus) cucurbitae (Coquillett, est. 1895). Male annihilation technique has been used in papaya for management of both B. dorsalis and B. cucurbitae. This system presents an opportunity to test the behavioral response of two species to a binary lure system in an economically important crop. Management using MAT to date has been typically done in a single lure format that targets one species with separate trapping materials, labor, and deployment. Given that B. dorsalis and B. cucurbitae are both routinely found in and around papaya growing areas, this study sought to understand the significance of visual and olfactory cues in resource location of papaya for both fruit fly species. It also aimed to test the application and optimization of a binary lure MAT system that would reduce the numbers of both fly species. In a series of behavioral experiments, I quantitatively measured the host resource use of B. cucurbitae on papaya and compared the sensory modalities used by two tephritids that are currently considered a “primary” pest (B. dorsalis) and an “occasional” pest (B. cucurbitae) of papaya. I recovered twenty times more adult wild B. cucurbitae flies than B. dorsalis flies from sentinel papaya fruits placed in the largest papaya growing area in the United States. Results of visual and olfactory experiments suggest that B. cucurbitae females are not primarily attracted to volatiles emitted by papaya fruit, but rather vision seems to be the main stimulus inducing landing and oviposition. Bactrocera dorsalis appears to be equally responsive to either olfactory or visual stimuli of papaya. These observations demonstrate a potential for behavioral control using visual mimics with B. cucurbitae. Furthermore, a synergistic approach using both chemical and visual stimuli to control mature male and female fruit flies shows real promise. I performed a series of field trials to evaluate a novel binary lure MAT for two species simultaneously, B. dorsalis and B. cucurbitae. The trials were conducted in a large papaya growing area using standard trapping methods to determine efficacy and optimization of a binary MAT system (SPLAT™, Specialized Pheromone and Lure Application Technology, ISCA Technologies, Riverside, CA) with a biopesticide (spinosad, Dow AgroSciences LLC, Indianapolis, IN). I found that a binary lure system may function as a generic MAT (ME + CL) against B. dorsalis and B. cucurbitae when populations of both species are associated in a cropping area. Binary lure formulation of SPLAT was optimized by increasing the amount of ME from 25.5% to 45% and decreasing the amount of CL from 10% to 8%. A single application containing both lures could potentially reduce labor, equipment and material costs by 50%. Following the results of the field trials, it was important to identify any potential interspecies dependent responses of B. dorsalis and B cucurbitae using novel binary lure MAT. In a series of cage test, the number of individuals in each species was manipulated to examine if the response changed when one species occurs in greater numbers than the other. I also evaluated male attractants ME + CL at varied ratios to understand the role each lure plays on the response and capture of each species. I found no interspecies interactions. Captures for both species were not different when each species was alone, in equal numbers, or when the other species was in greater numbers. Instead, the only factor that seems to influence capture rate was measured in cages with B. dorsalis. The response of B. dorsalis amplified considerably with increase in the amount of ME formulated into binary SPLAT mixture. Response of B. cucurbitae was not influenced in the same way by increasing the amount of CL. Maximizing ME and using a lower amount of CL in a binary lure MAT at the trap or station would provide the most benefit when B. dorsalis and B. cucurbitae are in equal numbers or B. cucurbitae is the dominant species. I further explored the potential horizontal transfer of insecticide of a binary lure MAT containing spinosad. The sprayable application, strong behavioral response to male lures, and mode of action including time to mortality induced by spinosad may facilitate horizontal transfer of insecticide. Using a series of laboratory tests, I recorded mortality of conspecific male and female flies exposed to primary fed males of B. dorsalis and B. cucurbitae. I found that horizontal transfer can occur in both males and females of both species. This transfer can occur from a single fed male to other individuals or a group of conspecifics resulting in mortality. The higher mortality of males relative to females is linked to the strong behavioral response, of males to lures. Horizontal transfers of spinosad may provide enhanced suppression of both males and females of two species in one location. Together, the results of these experiments demonstrate that use of a binary lure in papaya systems will effectively attract and kill both B. dorsalis and B. cucurbitae. Furthermore, use of a reduced risk insecticide such as spinosad, will lead to horizontal transfer and increased mortality in the populations of both species. Thus, deployment of a sprayable binary lure MAT system with reduced risk insecticide spinosad would reduce the costs associated with materials, equipment, and labor by 50% and lead to similar mortality in the field.
Captive Rearing And Semiochemcial Ecology Of Trichogramma Papilionis (hymenoptera: Trichogrammatidae)
(University of Hawaii at Manoa, 2020) Ali, Abdulla Nezar; Wright, Mark G.; Entomology
This study addressed aspects of mass rearing of Trichogramma papilionis (Hymenoptera; Trichogrammatidae), including the effects of varied colony founder size on wasp fitness, and the exploitation of the wasps to locate egg hosts in which to deposit thereof progeny. Effects of initial founder female number of T. papilionis were investigated using fitness parameters (emergency rate, sex ratio and fecundity) to quantify the effects of a severe bottleneck (single founder female) on 10 subsequent generations. Results showed that no significant difference for eggs laid per female over ten generations, suggesting that the imposed bottleneck did not result in reduced female fecundity for any founder population size. However, founder numbers did affect both the emergence rate and sex ratio of T. papilionis. Further investigation of the impacts of inbreeding on field performance of the wasps was discontinued as extremely limited host finding ability of the wasps was observed in some habitats. The emphasis of the work was thus shifted to elucidating the searching behaviors of T. papilionis in relation to chemical cues. The hypothesis that T. papilionis are attracted to host habitat by host plant or egg-associated volatile chemicals was tested. The response of T. papilionis females to olfactory cues from host eggs, host plants and induced plant volatiles were studied. The response of T. papilionis females to different info-chemical cues was tested in Y-tube olfactory assays. Wasps made a positive response to odors from corn earworm (CEW) eggs Helicoverpa zea (Lepidoptera: Noctuidae) compared with blank air, while there was a negative response to Ephestia kuehniella eggs (Lepidoptera: Pyralidae) compared blank air: T. papilionis females thus preferred odors from corn earworm eggs over the Mediterranean flour moth eggs. Further, the wasps were attracted to volatile emissions from sunn hemp Crotalaria juncea (L.) over maize Zea mays (L.), despite both plants infested with H. zea eggs. No preference was observed for plants not infested with H. zea eggs, suggesting T. papilionis showed a positive response to stimuli from sunn hemp plants that might be induced by H. zea oviposition. Chemical volatile collection and headspace analysis was conducted. Headspace analysis and thermal desorption and gas chromatography–mass spectrometry (TD-GCMS) was used to qualitatively and semi-quantitatively determine the difference in plant volatile organic components (VOCs) from Helicoverpa zea egg infested sunn hemp plants compared with intact sunn hemp plants and H. zea eggs only. TD is used as a preconcentration technique of VOCs for gas chromatography-mass spectrometry (GC–MS), making it useful to detect low-concentration analytes that would otherwise be undetectable. Results demonstrated that sunn hemp plants released 55 chemical volatiles with five compounds that were unique, or were emitted in higher concentrations, for plants infested with CEW eggs. These volatile compounds were consistent with linear alkanes, aldehydes, aromatics, polyterpene-related compounds, naphthalene derivatives, and ester-related compounds. High concentrations of anisole, β-myrcene, cis-butyric acid, trans-isoeugenol, and bis(2-ethylhexyl) phthalate were found in infested sunn hemp. The majority of GCMS peaks detected from H. zea eggs were consistent with phosphates, pheromone-related compounds, various natural products, a series of glycol-related compounds, and a series of fatty acid ester-related compounds. Several compounds were shared in sunn hemp samples and corn earworm eggs: anisole, β-myrcene, and bis (2-ethylhexyl) phthalate, but were detected in higher concentrations from the plants with H. zea eggs. Evaluation of the response and the performance of T. papilionis females in y-tube olfactory bioassays to single compounds, and blends of synthetic chemical showed that the wasps were significantly attracted to only two of the assayed chemical volatiles (anisole and bis(2-ethylhexyl) phthalate). Some concentrations of anisole and bis (2-ethylhexyl) phthalate were attractant to the wasps, whereas some concentrations of the other tested chemical compounds repelled the wasps. Wasps were attracted to a blend of anisole and bis(2-ethylhexyl) phthalate (25μL /100μL ratio) which is similar to the ratio of anisole to bis(2-ethylhexyl) phthalate detected in the (GC-DMS) chromatograph for C. juncea plants infested with H. zea eggs. No significant attraction to any other blend ratios of anisole and bis(2-ethylhexyl) phthalate was observed. Greenhouse and field experiments were conducted to determine whether the patterns observed in the y-olfactometer were consistent under less constrained conditions. The optimal blend identified above was initially tested in a greenhouse, and later in closed-canopy environments (under trees) and open habitat with no trees. The parasitism rate by T. papilionis wasps was significantly increased when the wasps were exposed to anisole and bis(2-ethylhexyl) phthalate blend in both greenhouse and outdoor trials (covered habitat), at least over short distance (up to 2m from the volatile sources). The findings presented in this dissertation underscore the importance of improving our understanding of how tri-trophic interactions (natural enemies- herbivores and host plants) interact to influence insect behavior, as well as the impact of variable environments, impact parasitoid wasps. The results may also contribute to finding a way to improve natural enemy efficacy in augmentative and conservation biocontrol efforts. Semiochemical cues can positively or negatively affect the response of parasitic wasps. This may provide an understanding of ecology that could facilitate achieving successful field parasitism and thus enhanced pest management.
Ecological management of insect pests using cover crops in field crops and vegetables
(University of Hawaii at Manoa, 2013-08) Manandhar, Roshan
This dissertation researched diversified cropping systems created through habitat management techniques, exploring whether these habitats would alter pests' behavior and/or enhance beneficial insects, and contribute to suppress pest and disease complexes in corn production systems. An exploratory study through small-scale field experiments determined sunn hemp (Crotalaria juncea) as the potentially the most suitable species for further study. In the preliminary studies, sunn hemp intercropping reduced incidence of hopperburn and Maize mosaic virus (MMV) symptomatic plants caused by Peregrinus maidis feeding, and increased parasitism of Helicoverpa zea eggs by Trichogramma spp. on the corn silks. The reduced incidence of hopperburn and MMV was attributed to an increase in P. maidis within-field activity, resulting in reduced initial colonization on corn plants. The results showed a suitable intercrop might be useful for management of persistent viruses, which are usually considered unmanageable by habitat management to cropping systems. On the basis of these preliminary studies, experiments were conducted in large-scale field with a higher corn-to sunn hemp intercropping ratio to validate results and possibly contribute new pest management options for large-scale corn production systems. Increase in within-field P. maidis activity with resulting in lower incidence of MMV symptomatic plants in the sunn hemp-intercropped treatments were consistently similar to results that were obtained from small-scale field experiments. This strategy may contribute an important component of integrated pest management for reducing spread of persistently transmitted viruses in large-scale corn production systems. Greater parasitism of H. zea eggs by Trichogramma spp. in sunn hemp-intercropped treatments was consistently similar to that obtained from small-scale field experiments. These results suggested growing strips or patches of suitable cover crop may help in sustaining the populations of beneficial insects at the time of pest outbreaks. Augmentative biological control (releases of Trichogramma pretiosum in corn monoculture) resulted in a greater parasitism of H. zea eggs, and increased ear yield compared to habitat management (sunn hemp-intercropped). This result suggested H. zea management is important component to achieve economic yield and augmentative biological control is a more effective tool than the habitat management in cornfields.
Foraging response of female Bactrocera dorsalis (Hendel) to a fruit fly protein food attractant
(University of Hawaii at Manoa, 2013-08) Chou, Ming-Yi
Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) causes serious economic loss for papaya (Carica papaya L.) production in Hawaiʻi through direct fruit damage and restriction of export commodities. Suppression of female flies was a challenge until a protein-based bait contains reduced risk insecticide spinosad became available, GF-120 NF Fruit Fly Bait (GF-120; Dow AgroScience, Indianapolis, IN). This bait provides an environmentally sound alternative to conventional cover spraysof organophosphate insecticides. Factors that influence the attractiveness of protein bait include chemical composition, visual stimuli, and competing volatiles from host fruits. This dissertation focuses on biological factors that affect the foraging response of female B. dorsalis to volatiles emitted by protein bait. Female reproductive state and dietary experience are two biological variables that shape the manner in which a fly searches for and responds to essential resources such as food and egg-laying sites. The experiments reported in this dissertation were conducted in order to assess the influence of physiological states on the response of female B. dorsalis to protein bait in papaya orchards. In Chapter 1, baseline information on key morphological characters in B. dorsalis ovarian development and the associated morphometric parameter of each oogenesis stage is collected. Four oogenesis stages include previtellogenesis, vitellogenesis, gravid and parous. In Chapter 2, field observations were conducted to determine reproductive states of B. dorsalis females (using ovarian developmental stage as an indicator) that respond to 2 two protein bait trapping devices: visually enhanced attract-and-kill bait stations termed papaya leaf mimics (PLMs) treated with GF-120 and dome traps containing torula yeast solution. Females with ovaries at previtellogenesis stage and egg laying females are the two main classes that responded to protein bait. Visual stimuli from the bait stations enhanced the response of immature females to protein bait but this effect was not found in egg-laying females. Yellow color also increased the capture of females with greater egg loads compared to those captured by green bait stations. This is an important finding for improved fruit fly management because reducing numbers of egg-laying females within an area results in lower fruit infestation. The physiological state of foraging flies determines the level of food searching behavior. In Chapter 3, the effects of female age and dietary history on the propensity of B. dorsalis to alight on protein bait were quantified. One week old females exposed to papaya as a diet source for 4 d in the first week of adult life showed a significantly greater propensity of alighting on GF-120 protein bait than females fed on a protein or sugar diet. Delay of ovarian development from feeding on a sugar only diet resulted in significantly higher response of 4 week old females to protein bait than females fed on papaya or protein. On the contrary, ovarian development in papaya fed females was not significantly different than that of protein fed females. Feeding on papaya during weeks 2 to 4 of adult life increased the response of female flies to protein bait at a lesser level than for 1 week old females. These results are evidence of the possible physiological profile of females attracted to protein bait in the natural environments. In addition, previous exposure to papaya fruit enhanced the response of females to papaya compared to females without the experience. This is a finding that suggests sanitation practice of removing culled fruit not only removes a breeding source but may also reduce the number of females re-entering orchards. Studies conducted in this dissertation are the first documentation of the response of egg-laying female B. dorsalis to protein bait under natural and semi-natural conditions. Results suggest that protein baits such as GF-120 attract females with developing ovaries as well as egg-laying females. In addition, fruit-based diet enhances the response of female B. dorsalis to protein bait and host fruit stimuli.
Developing a monitoring tool to understand the seasonal dynamics and management techniques to estimate a sampling plan for Xylosandrus compactus (Eichhoff) in Hawaiʻi
(University of Hawaii at Manoa, 2010-12) Greco, Elsi Burbano
The potential damage caused by the invasion of exotic ambrosia beetles to Hawaiʻi is one of the biggest concerns for the coffee, forestry and ornamental plant industries. Most of these invasive beetles are from temperate areas and find a suitable environment for reproduction and survival in Hawaii, which is favored by climatic conditions, presence of alternate hosts and the lack of natural enemies. The black twig borer, Xylosandrus compactus (Eichhoff), is an important coffee pest and native forests in Hawaiʻi. This ambrosia beetle is highly polyphagous, reported from >200 hosts, including native plants such as the valuable timber species Acacia koa. This dissertation addressed the response of X. compactus to semiochemicals which were used to determine the beetle flight seasonality, phenology of the black twig borer in coffee plantations, and development of a sequential sampling plan for management decision making. It was demonstrated that Japanese beetle traps baited with ethanol can serve as monitoring tool for the black twig borer, and ethyl alcohol baits yielded higher capture rates than eugenol and α-pinene. It was also demonstrated that the repellents verbenone and limonene, significantly reduced trap catches of black twig borer. Ethanol baited Japanese beetle tras were used to assess the seasonal fluctuation of black twig borer throughout the year. Data obtained from trapping demonstrated the peak beetle flight periods, which were used as an predictor of damage levels for accurate timing of control measures. Elevation and season were significantly related with the number of beetles captured and level of infestation. Taylor's Power Law analysis showed an aggregated infestation of X. compactus in coffee fields. The density of infested branches per sampled unit can be estimated using the sampling plan and compared with the action threshold level to make a management decision. Enumerative sampling allows estimation of the black twig borer abundance with specified precision, providing researchers with a valid tool for the study of this pest in coffee. Three species of scolytines were detected attacking coffee berries in Hawaiʻi, Xylosandrus compactus, Hypothenemus obscurus and H. hampei. The biology, behavior and management of these three species are discussed.
Meta-population dynamics and evolution of Diachasmimorpha tryoni (Hymenoptera; Braconidae), a purposefully released parasitoid of ceratitis capitata (Diptera: Tephritidae), in Hawaiʻi
(University of Hawaii at Manoa, 2011-05) Vorsino, Adam Eric
The meta-population and evolutionary dynamics of the Australian biocontrol agent Diachasmimorpha tryoni, a parasitoid of Ceratitis capitata, was investigated due to its association with a non-target host, Eutreta xanthochaeta and competitive interaction with Fopius arisanus in Hawaii. Twelve polymorphic microsatellite loci were characterized and used in combination with sequence data to profile D. tryoni's evolution within Hawaii and between Hawaii and Australia. Using both contemporary and historic collections it was found that D. tryoni has evolved significantly from its founding population, but no predicted population was significantly associated with that of the non-target host. The interaction between D. tryoni and its competitor was assessed using a combination of population genetic inference and ecological niche modeling techniques. This interaction was shown to have the greatest evolutionary influence on D. tryoni in Hawaii through competitive exclusion into upper elevation habitat, as characterized by E. xanthochaeta. Augmentative releases of D. tryoni were also genetically modeled using museum specimens to assess the influence that a mass release may have on the evolutionary dynamics of a naturalized population. The majority of individuals post-augmentation were found to be genetically associated with the released population, but hybridization between the two populations was observed. This data also implies local population recruitment and population genetic structural dilution, suggestive of a Reverse Bottleneck following augmentation. The influence of heterosis on the interaction between mass released and naturalized D. tryoni was also measured. Employing a combination of mate selection trials, molecular genotyping, and fitness measurements, our results were capable of documenting the hybridization of the released and wild populations, the fitness of the hybridization interaction, and female mate choice. These analyses reveal that the interactions between two moderately differentiated populations, as would be the case during an augmentative release, are significant. The techniques employed herein can be used to understand the influence a competing organism, or a mass released agent, may have on a biocontrol agent prior to both classical, or augmentative biocontrol introduction.
The biogeography, phylogenetics, and population structure of Hawaiian lepidoptera, with a focus on the genus omiodes (crambidae)
(University of Hawaii at Manoa, 2011-12) Haines, William Parker
Hawaiian Lepidoptera (moths and butterflies) represent a major biodiversity component, with almost 1000 described species, but relatively little is known about their patterns of diversification. This dissertation explored broad diversification patterns of Hawaiian Lepidoptera, then narrowed to focus a single genus, Omiodes (Crambidae), particularly of interest because of its host plant associations. Five species feed only on non-native banana, presumably due to rapid speciation within the last 1200 years. In Chapter 1, I related lepidopteran biodiversity to predictor variables (area, age, isolation, and topographic heterogeneity) on the island level. The species area relationship (SAR) of Lepidoptera in Hawaii was steep compared other archipelagoes and area, age, and topographic heterogeneity were positively related to diversity. Chapter 2 explored the relative contributions of colonization and diversification to taxonomic disharmony. Binomial probabilities showed that only one family (Tortricidae) was overrepresented among native lineages compared to a global species pool. I found no relationship between colonization success and body size or host specificity, but interestingly, colonization success of native and non-native species was correlated. Among 58 Lepidoptera lineages, diversification was inversely related to mean body size, likely because small moths are poorly adapted for active dispersal. In Chapters 3 and 4, I reconstructed molecular phylogenies for Omiodes species worldwide and within Hawaii. Omiodes worldwide fell within a well-supported clade that included the type species. The center of origin for Omiodes appears to be the Paleotropics, giving rise to both Hawaiian and neotropical clades. Within Hawaii, I estimated divergence times of 3.2 MYA for the entire lineage, and 1.9 MYA for banana-feeding taxa, inconsistent with rapid speciation. Finally, in Chapter 5, I explored intraspecies gene flow in eight species of Hawaiian Omiodes, and found considerable variation among species in terms of population structure (ΦST). Some species showed no evidence of isolation related to islands, and others showed nearly complete isolation. Gene flow was lowest in species that were rare, host-specific, and limited to small historical ranges. It is likely that speciation in Omiodes has occurred primarily allopatrically, but host specificity may play a role by selecting against against long-distance dispersal.
Applied conservation research of the wēkiu bug in Hawai΄i: life table analysis, population genetics, and phylogenetics create a holistic view of a rare and unique species
(University of Hawaii at Manoa, 2012-05) Eiben, Jesse Alan
The wekiu bug (Nysius wekiuicola Ashlock and Gagné 1983) is a flightless carnivore endemic to the dormant Mauna Kea volcano, on the Big Island of Hawaii. Wekiu bugs only occur between 3,350m (11,500ft) and the summit at 4,205m (13,796ft) in an environment described as high alpine desert. Remarkably, the main nutrient input to the summit comes from aeolian deposition of arthropods blown in from lower elevations. The wekiu bug‟s habitat is subject to dramatic temperature extremes, with daily fluctuations in their microhabitat caused by solar daytime heating and rapid evening cooling. The wekiu bug was, until fall 2011, a candidate for listing under the Endangered Species Act. Detailed ecological data of the wekiu bug are necessary for informed management decisions. I briefly present an overview of insect conservation research and the field‟s current status in Hawaii as a primer to the research conducted for this dissertation. I investigated unknown aspects of the wekiu bug‟s life history using life table experiments and degree day modeling, showing how the wekiu bug can develop in its harsh natural environment. They have a low reproductive output in captivity, develop most quickly at 30-32°C, exhibit an intrinsic rate of increase (r) of 0.045 in field simulations, and require 622 degree days for one generation. This developmental requirement is only achieved for a maximum of 8.5 hours of solar heating on Mauna Kea. This lab-based study helped explain field observations and trapping patterns. Also, using population genetic analyses of mtDNA haplotype diversity, I describe the potential impacts of habitat disturbance and ecosystem alteration in two distinct populations. Finally, I investigated the evolution of the wekiu bug within the Nysius lineage using DNA sequence from 29 Nysius species. Its closest relatives are seed feeding Nysius, on Maui and Hawaii islands, and there is considerable taxonomic revision needed in the genus. In the appendices of this dissertation, I present a pictorial key of the Hawaiian Nysius for identifying the Nysius in Hawaii, and I provide a summary of the technical reports of wekiu bug monitoring from 2005-2011, with maps for resource managers‟ use.
Biological and molecular characterization of caecum-associated symbionts in the Pentatomidae
(University of Hawaii at Manoa, 2008) Prado, Simone S.
The Pentatomidae is one of the largest families within the suborder Heteroptera (order Hemiptera), with over 4000 described species within eight subfamilies. Stink bugs are major pests of economically important crops worldwide including soybeans, rice, pecan, cocoa and macadamia nuts. Relationships between microorganisms and insects have been previously studied, but the majority of these associations remain poorly understood. In this dissertation I present molecular data showing that Nezara viridula, Acrosternum hilare Murgantia histrionica, Euschistus heros, Chlorochroa ligata, C. sayi, C. uhleri, Plautia stali and Thyanta pallidovirens harbor a common dominant caecum-associated bacterial symbiont in their midgut. I also show that oral rather than transovarial transmission occurs by detecting the symbiont on eggshells after nymphs had hatched, instead of detecting symbionts in female ovarioles. Additionally, I demonstrated that these symbionts are polyphyletic suggesting that replacement of the symbiont may occur over time. Phylogenetic placement showed the pentatomid symbionts were associated with the plant pathogens Erwinia and Pantoea. Using a demographic approach I analyzed the effect of egg masses surface sterilization and temperature on the symbiont maintenance and on insect development of the pentatomids N. viridula, A. hilare and M. histrionica. Here I demonstrate that maintenance of the symbiont was affected by high temperature and egg mass surface sterilization for the species N. viridula, A. hilare and M. histrionica. N. viridula's reproduction parameters were not significantly different between the surface sterilized and control treatments at three temperatures, however no reproduction was observed at 20°C of the surface sterilized treatment. Survivorship and reproductive parameters for A. hilare were negatively affected by surface sterilization of egg masses and for higher temperatures. Conversely, no effect was observed for M. histrionica. Curiously, M. histrionica had lower rates of positive insects for the symbiont at 25°C than A. hilare. Here I suggest that the degree of mutualism of this association for pentatomid species is variable, given the fact that A. hilare requires its symbiont for adequate development, while M. histrionica's symbiont may not be significant in development of the host insect and N. viridula is not affected by deprivation of its gut-associated symbiont.
Non-target impacts of introduced parasitoids and validation of probabilistic risk assessment for biological control introductions
(University of Hawaii at Manoa, 2008) Kaufman, Leyla Valdivia
Field surveys and partial life table studies were conducted to assess apparent mortality and marginal attack rate, respectively. Field surveys of larvae were conducted at eight different sites throughout the Hawaiian Islands, parasitism rates by individual parasitoid species varied significantly among study sites of varying ecological conditions. Adventive parasitoids rather than purposely introduced ones were responsible for the majority of U. stellata apparent mortality. Results from the life table studies showed that predation) was the major larval mortality factor at all study sites and that parasitism contributed minimally to total mortality. The two purposely introduced parasitoids were present at high altitude, in relatively undisturbed sites.
A comparative study of the bionomics of Peregrinus maidis (Ashmead) and its egg-predator, Cyrtorhinus mundulus (Breddin) and the toxicity of several contact and systemic insecticides to the two species
(University of Hawaii, Honolulu, 1954) Verma, Jit
Biological studies on the Nitidulid beetles found in pineapple fields
(University of Hawaii, Honolulu, 1934) Schmidt, Carl
The biology, distribution and control of ants in Hawaiian pineapple fields
(University of Hawaii at Manoa, 1933) Phillips, John
Effects of an entomogenous nematode, Neoaplectana carpocapsae Weiser, on the Formosan subterranean termite, Coptotermes formosanus Shiraki, with ecological and biological studies on C. formosanus
(University of Hawaii at Manoa, 1975) Fujii, Jack K.

Browse

Recent Submissions