M.S. - Entomology

Permanent URI for this collectionhttps://hdl.handle.net/10125/1833

Browse

Now showing 1 - 20 of 43

Autodissemination of Beauveria bassiana as a strategy to manage melon flies (Zeugodacus cucurbitae) and oriental fruit flies (Bactrocera dorsalis) in Hawai‘i
(University of Hawai'i at Manoa, 2025) Pennington, Sarah Kirstin; Shikano, Ikkei; Entomology
Fruit flies (Diptera: Tephritidae) are major agricultural pests globally, capable of causing devastating crop losses. These pests have restricted Hawai‘i’s fruit export opportunities, caused millions in annual crop losses, and discouraged fruit production due to high control costs. The ongoing pressure from fruit flies in Hawai‘i highlights the limitations of current control strategies and the urgent need for new approaches. Entomopathogenic fungi have lower environmental impacts than chemical insecticides, and decades of research show that they can cause high mortality in tephritids. Entomopathogenic fungi autodissemination devices are a promising developing innovation for tephritid management. By using male-attracting, species-specific parapheromone lures in the autodissemination device, male flies can act as vectors to transfer fungal spores to sexually-mature females. Our lab developed a novel oil-based formulation of entomopathogenic fungi Beauveria bassiana and a 3D-printed autodissemination device. In this study, I tested the ability of our autodissemination device to suppress populations of the two most abundant invasive tephritid species in the state- melon flies (Zeugodacus cucurbitae) and oriental fruit flies (Bactrocera dorsalis). Current tephritid control strategies rely heavily on insecticide-laced bait sprays, mainly containing Spinosad, leading to elevated resistance levels in several wild melon fly and oriental fruit fly populations in Hawai‘i. First, I used lethal concentration assays to assess population-level variation in B. bassiana and Spinosad susceptibility in wild and laboratory melon fly and oriental fruit fly colonies. I found B. bassiana could induce high mortality in both highly Spinosad resistant and susceptible melon fly colonies. Next, I conducted laboratory trials to 1) evaluate the autodissemination device’s ability to facilitate horizontal transfer of spores from male to female flies, and 2) determine if the autodissemination device can cause significant mortality in melon fly and oriental fruit fly populations. Results showed clear evidence of horizontal spore transfer and that the autodissemination device could induce significant mortality in both species. Finally, I conducted four field trials to assess the ability of our device to reduce melon fly and oriental fruit fly populations on commercial farms in Hawai‘i. In three field trials, we demonstrated that the autodissemination device could reduce melon fly populations. However, in the one field trial targeting oriental fruit flies, fly populations were not reduced- possibly because of the shorter treatment period and differing farm management practices. Together, these results demonstrate that our autodissemination device can reduce tephritid fruit fly populations, and could be a valuable addition to current management strategies.
Prevalence of novel RNA viruses: Pheidole megacephala viruses (PmegV) in the invasive big-headed ant, Pheidole megacephala on Oʻahu island, Hawaiʻi and Successful RNA virus transmission using alginate hydrogels as a delivery system for Pheidole megacephala virus 3 (Picornaviridae: Picornavirales) to target invasive ants, Pheidole megacephala, and resulting mortality.
(University of Hawai'i at Manoa, 2025) Chang, Joey Yin-Xin; Wright, Mark; Entomology
Invasive ants pose a significant threat to global biodiversity, particularly in ecologically sensitive island ecosystems such as Hawaiʻi. Pheidole megacephala (Fabricius), the African big-headed ant, is one of the world’s worst invasive species and has become dominant in disturbed environments, where it disrupts food webs, supports pest outbreaks, and alters soil ecosystems. Conventional control methods offer limited long-term success and pose risks to non-target species, highlighting the need for sustainable, targeted alternatives. Biological control using RNA viruses represents a promising solution, with Polycipiviridae viruses demonstrating host specificity and pathogenic potential. In Hawaiʻi, where P. megacephala dominates urban and disturbed habitats in the absence of natural enemies, three novel positive-sense single-stranded RNA viruses, Pmeg V1, V2, and V3 were recently discovered, opening new avenues for biological control. This study first conducted an island-wide survey of P. megacephala colonies across Oʻahu (n=25), revealing that 56% of colonies harbored at least one virus, with Pmeg V2 was most prevalent (52%), followed by Pmeg V1 (36%) and Pmeg V3 (12%). Due to its low natural prevalence, Pmeg V3 was selected for experimental delivery to assess its infectivity and effects on colony health. We next evaluated the efficacy of an alginate hydrogels system for introducing Pmeg V3 to ten uninfected P. megacephala colonies. Reverse transcription-polymerase chain reaction (RT-PCR) confirmed successful viral transmission and tagged RT-PCR verified replication within worker ants. While Pmeg V3 infections reached queens and brood by Day 17, replication was limited to workers. Kaplan-Meier survival analyses showed significantly reduced survival in four of ten treated colonies. These findings support the potential of alginate hydrogels as an effective viral delivery system and establish foundational evidence for developing virus-based biological control strategies against invasive P. megacephala populations.
Gut microbial communities of Plutella xylostella vary among Hawaiian island populations
(University of Hawai'i at Manoa, 2024) Montoya-Pimolwatana, Maya Louise; Jani, Dr. Andrea; Shikano, Dr. Ikkei; Entomology
It is well-established that for many species of Lepidopterans, population, along with various associated environmental effects such as host diet and local environments, has a significant influence over the host's community composition. Nonetheless, many insecticide-mediated resistance studies focus solely on lab-reared resistant lines, looking for taxa that convey resistance through functionality or an increase in abundance, often neglecting multi-population studies. Thus, the impact of population on the host's microbial response to insecticide application is poorly understood. This project seeks to identify if population impacts the bacterial diversity and community composition of the highly insecticide-resistant insect Plutella xylostella by analyzing the bacterial communities of field-caught specimens from several populations across Oʻahu, Hawaii and then rearing an F1 generation in the lab to check for dissimilarities in the bacterial communities among control populations and among populations exposed to sublethal and lethal doses of Spinosad. Our results showed that population strongly influences bacterial community composition and richness, with abundant taxa varying among populations and each lab-reared population exhibiting a distinct community composition. Moreover, when subsets of the lab populations were exposed to lethal and sublethal doses of Spinosad, the distribution of bacterial taxa varied among populations, with no uniform pattern. These results emphasize the importance of accounting for population-specific factors in insecticide resistance research and the necessity of integrating field and laboratory studies to better understand the role of the microbiome in insecticide resistance.
Community Ecology of Two Pest Ant Species in Hawaiʻi and a Potential Advancement in Microbial Ant Biocontrol
(University of Hawai'i at Manoa, 2024) Lawrence, John Adam; Tay, Jia-Wei; Entomology
Many invasive ant species have become pests of global status and have had an enormous suite of economic and ecological impacts. In Hawaiʻi, one of the few places on Earth thought to completely lack native ants, these impacts are especially severe. Four species present, Pheidole megacephala, Anoplolepis gracilipes, Linepithema humile, and Wasmannia auropunctata, are on the IUCN-GISD list of the 100 worst invasive species. While P. megacephala established in the late 19th century, W. auropunctata arrived in the late 1990s. Despite this comparatively recent introduction and proactive treatment regimes, W. auropunctata continues to spread throughout the archipelago and has become a serious economic, ecological, and public health hazard. There are concerns that W. auropunctata could expand into the range of P. megacephala, either through competitive displacement or by moving into vacated treated areas. To test this possibility, I evaluated intraspecific aggression between 16 P. megacephala nesting sites on Oʻahu to better understand its social structure. Upon discovering that P. megacephala displays nonsignificant levels of intraspecific aggression, I performed laboratory confrontations between P. megacephala and W. auropunctata to determine whether numerical superiority and lack of intraspecific competition could enable P. megacephala to resist encroachment from W. auropunctata. Interspecific laboratory confrontations revealed that W. auropunctata overwhelmingly dominated P. megacephala.This finding suggested the need to develop flexible pest ant treatment technologies to account for potential shifts in the community composition of ants. To address this need, I attempted to integrate +ssRNA ant viruses identified within P. megacephala and W. auropunctata populations into alginate hydrogel beads. The detection of integrated hydrogels revealed that a P. megacephala-associated virus could be successfully integrated into hydrogels. Detection attempts using a W. auropunctata-associated virus were inconclusive. As ants are necrophobic insects, the palatability of gels conditioned using a homogenate of 25% sucrose solution and ant tissue was examined. Despite the presence of ant tissues within the hydrogel beads, both species exhibited attraction to these tissue-integrated beads. While additional work is needed to better understand how to efficiently integrate viruses into hydrogels and whether the consumption of integrated hydrogels leads to infection, these results suggest that hydrogels are a potential vehicle for the microbial biocontrol of pest ants.
Larvicidal activity and oviposition preference of Aedes albopictus (Diptera: Culicidae) induced by Beauveria bassiana (Hypocreales: Cordycipitaceae), and an investigation of mosquito abundance drivers in Nu‘uanu Valley, Oahu, Hawai‘i
(University of Hawai'i at Manoa, 2022) Kirsch, John Mitchell; Tay, Jia-Wei; Entomology
Establishment of Aedes albopictus (Skuse) (Diptera: Culicidae) on the Hawaiian Islands has led to endemic Dengue virus transmission and potential for future arbovirus outbreaks. Current pest management tactics such as larval habitat reduction and chemical pesticides have failed to alleviate the biting pressure of the mosquito, calling for new, 21st century Integrated Pest Management (IPM) strategies using biological control. A promising mosquito biological control agent is the entomopathogenic fungus, Beauveria bassiana (Balsamo-Crivelli) Vuillemin, which allows chemical-free and environmentally safe vector management. The first chapter of this thesis is a mini-review on B. bassiana and its current use on Ae. albopictus. The second chapter is composed of a two-part experiment investigating the mortality of Ae. albopictus larvae exposed B. bassiana using Mycotrol® ESO and an analysis of wild adult oviposition behavior in response to different fungal concentrations. The third chapter explores how various factors influence the abundance of Ae. albopictus in the Nu‘uanu Valley by constructing generalized linear models. Results of a Kaplan–Meier survival analysis revealed that larval mortality was concentration dependent with higher concentrations of the fungus causing more rapid and increased mortality. We observed inverse relationships between the concentration of B. bassiana and egg likelihood and egg abundance. Because of differences in site mosquito abundance, we evaluated population drivers including potential larval habitats, abiotic environmental factors, and four urbanization measurements. The results indicated Ae. albopictus are most prevalent in areas containing high densities of small buildings. Elevation and density of potential natural breeding sites were not significant factors contributing to abundance of Ae. albopictus. In conclusion, we demonstrate larval control using a mycopesticide, a potential change in ovipostional behavior induced by the fungus, and Ae. albopictus are most prevalent around low elevation, single family home residential areas with available breeding habitats. The use of B. bassiana can be integrated with existing integrated vector management strategies to better control vectors and to minimize the spread of insecticide resistance in mosquito populations. Additionally, public health agencies can provide better targeted messaging, outreach, and education, before the next arbovirus outbreak in Hawai‘i.
The effects of insectary plants on natural enemy and pest abundance, and pest dispersal within cabbage agroecosystems in Hawaiʻi
(University of Hawai'i at Manoa, 2023) Armstrong, Kevin Matthew; Shikano, Ikkei; Entomology
Habitat manipulation is the foundation of agricultural systems. Fields are cleared and leveled, waterways are diverted, soils are amended, and crops are cultivated. Often a single field corresponds to a single crop, regardless of size. This concentration of resources often leads to pest outbreaks. The massive increase in the use of conventional pesticides in the 1960-1980s, along with habitat destruction to expand farming areas, has decimated insect populations worldwide. It has also raised environmental and human health concerns. Growing demand for sustainable alternatives has led to the development of organic pesticides and support for research into biological control. While organic pesticides remain an extremely useful tool, insecticide resistance amongst certain species has become a problem. Biological control can be an environmentally sound and effective means of reducing or mitigating pest outbreaks. Natural enemies can be augmented to agricultural systems or conserved by increasing plant diversity in agroecosystems. The implementation of conservation biological control aims to mitigate the consequences of habitat loss, ecosystem simplification, and disturbance and often involves adding insectary plants to farm production areas. Insectary plants provide habitat and nutritional resources for natural enemies (predators and parasitoids). Increasing the populations of natural enemies has been shown to increase top-down control of pest populations. Non-consumptive effects, the non-lethal effects of natural enemies, have also been shown to induce fitness costs on pest populations and have become a focus area within entomological research. In Hawaiʻi, Plutella xylostella, the diamondback moth (DBM) is the major pest of concern for Brassica producers. The dominant DBM parasitoid found throughout the island chain, Cotesia vestalis, fails to control DBM below economic thresholds, causing growers to rely on a rotation of insecticides for effective control. The research described in this thesis focuses on using insectary plants to maximize the impact of parasitoids on the top-down control of cabbage pests while also exploring the nuanced relationship between C. vestalis and DBM. In the lab, I evaluated the influence of C. vestalis on the movement of DBM. In the field, I compared the impacts of natural enemies in organic and conventional (with regards to pest management) cabbage production systems when prey access was manipulated to test the sensitivity of DBM to its predators and to further investigate how DBM movement was influenced by natural enemies.
Developing a Fungal Based Trapping Station for the Control of Fruit Flies (Diptera: Tephritidae) in Hawaii
(University of Hawaii at Manoa, 2023) Streit, Christian; Shikano, Ikkei; Entomology
Fruit flies (Diptera: Tephritidae) are a cosmopolitan species with many members of this family known to be economically significant pests. Research to understand the lifecycles and unique behaviors of these flies have been important to exploit critical points of development to control their populations. Many management strategies have been proposed, studied, and implemented across the world and have been met with success. But, with the ability of these flies to disperse, not all methods are applicable or successful in all regions. Entomopathogenic fungi are being studied in conjunction with the Tephritidae to determine efficacy against all life stages. Entomopathogenic fungi are capable of inducing high rates of mortality in adult fruit flies. The limiting factor of entomopathogenic fungi is its susceptibility to UV radiation. For this reason, it is widely used as a soil drench. Development of a product that incorporates entomopathogenic fungi to target adult fruit flies would be far more efficacious, adding one more tool to a widening array of management tools. Multiple stages of testing and development were performed, starting with determining the efficacy of Beauveria bassiana against three invasive tephritid fruit flies in Hawaii: Bactrocera dorsalis, Ceratitis capitata, and Zeugodacus cucurbitae. After confirming that B. bassiana kills adult fruit flies, we determined the lethal concentrations and developed a formulation that would be effective in a passive bait station, which included incorporation of lures and thickening agents.The effectiveness of each addition or modification to the formulation was assessed by measuring the mortality of exposed flies and the numbers of spores they picked up. The developmental goal of creating a formulation that could be vectored and dispersed across a population via horizontal transmission was confirmed, at least in lab cage trials. This fungal formulation could potentially be used as a new IPM tool for the control of tephritid fruit flies in both conventional and organic cropping systems.
Dietary Effects Of Prosopis Pallida On Apis Mellifera Health In Hawai‘i
(University of Hawaii at Manoa, 2023) Hausler, Daniel; Wright, Mark G.; Entomology
Pollen is a honey bee’s primary protein and lipid source and the availability, quality, quantity, and diversity of a bee’s pollen diet determine its individual health and, therefore, the overall health of the entire colony. Common kiawe (Prosopis pallida, Fabaceae) grows in the arid valleys of the leeward regions of all the Hawaiian islands and is a widely available food source for honey bees. This study aimed to determine the impact of kiawe pollen nutrition on colony health. To address this, I identified bee-collected pollen and analyzed its nutritive quality individually from apiaries on O‘ahu and Maui over a period of 14 months. Pollen was collected monthly, sorted by color as a proxy for species, and total proteins and lipid content quantified. Colony health metrics, including brood quality, frame occupancy of hive bees, and varroa and small hive beetle numbers, were also assessed monthly. Results showed there is spatial and monthly variation in kiawe pollen’s total protein and lipids, as well as a variation in hive health metrics and bee-collected pollen diversity. On Maui, SHB levels never significantly differed from each other, and were highest in June (10.12 ± 1.78). SHB levels on O‘ahu were highest in April (48.3 ± 7.61) while percent varroa mite infestation on O‘ahu was highest in January (5.67 ± 1.32). Mean brood quality was significantly higher on Maui (81.41 ± 0.43) compared to O‘ahu (78.33 ± 0.49). Also, mean frames of bees were significantly higher on Maui (14.73 ± 0.20) compared to O‘ahu (5.35 ± 0.11). Lipids levels were highest on Maui in June (14.28 ± 0.22 mg/g pollen) and highest on O‘ahu in September (15.48 ± 2.07 mg/g pollen), while protein levels on Maui were highest in January (326.28 ± 11.55 mg/g pollen) and highest on O‘ahu in February (361.53 ± 23.09 mg/g pollen). Additionally, the proportion of kiawe pollen in the homogenate (average percent total from six, 25 mL subsamples) increased during the kiawe blooming seasons (percentage was highest in March with 46.47 ± 6.34%) but these months did not display any change in hive health. Kiawe macronutrient quality did not significantly impact hive health metrics and hive health seemed more influenced by the absence or presence of varroa mites, showing that hives on O‘ahu are much more stressed than hives on Maui.
Fumigant Toxicity of Essential Oils Against Frankliniella occidentalis, F. insularis (Thysanoptera: Thripidae), and Solanum lycopersicum (Solanceae) as Affected by Polymer Release and Adjuvants
(University of Hawaii at Manoa, 2022) Gharbi, Karim; Tay, Jia-Wei; Entomology
Some species of thrips have become significant agricultural pests due to their cosmopolitan distribution, feeding damage and vectorial capacity for plant viruses. However, control of this pest is complicated by their life cycle and resistance to conventional insecticides. I sought to explore a novel method of thrips control that addressed these resistance mechanisms by applying essential oils as fumigants. These essential oils included (R)-linalool, racemic linalool, or a binary combination of (R)-linalool with one of twelve other oils (i.e., peppermint, cedarwood, neem, clove, coconut, jojoba, soybean, olive, α-terpineol, 1,8-cineole, trans-anethole and (R)-pulegone) with distilled water as a control. Essential oils were conditioned into hydrogels and exposed to a pesticide resistant species of thrips (Frankliniella occidentalis), a pesticide naive species (Frankliniella insularis), and a host plant of the former (Solanum lycopersicum). Thrips and tomatoes were first exposed separately in in vitro trials, and then together in caged-plant trials. Pure (R)-linalool and its binary mixture with peppermint oil were the most toxic to both species of thrips and tomatoes in in vitro trials. However, caged-plant trials revealed a greater level of resistance to essential oil fumigation than that predicted by in vitro trials. This resistance was attributed to behavioral resistance mechanisms precluded by in vitro trials. While certain essential oils have demonstrated potential as alternatives to conventional insecticides, glasshouse and field trials are necessary to fully quantify the extent to which the life history traits of thrips contribute to bioinsecticide resistance.
Trap Cropping For Bottom-up And Top-down Control Of Diamondback Moths (Plutella Xylostella) In Hawai‘i
(University of Hawaii at Manoa, 2021) Pugh, Morgan Elizabeth; Shikano, Ikkei; Entomology
Plutella xylostella, the diamondback moth (DBM), is a detrimental pests of many plants in the family Brassicaceae. Populations of DBM have become resistant to many types of pesticides. My thesis investigated the use of trap crops for the bottom-up and top-down control of DBM. The first research chapter examined the effects of putative dead-end trap crops on Hawaiian DBM. The second research chapter examined the role of the naturalized weed, Virginia pepperweed (Lepidium virginicum) on the behaviors of DBM and their natural enemies.To determine a suitable dead-end trap crop for use against DBM on cabbage (Brassica oleracea cv. K-K Cross) in Hawai`i, a series of larval feeding, oviposition, and survival experiments were conducted. The plants tested were Barbarea verna and two varieties of Lepidium sativum. All three plants have shown dead-end properties against DBM in North America and Europe. However, I found that Hawaiian DBM populations from O`ahu and Kaua`i behaved differently from these previous studies. The DBM populations used in this study only prefered to oviposit on one variety of L. sativum relative to cabbage, and showed no preference for the other two plants. More importantly, both DBM populations survived from egg to adult on all of the “dead-end” trap crops, just as well as they did on cabbage. Next, I examined the effects of L. virginicum on DBM feeding and oviposition behavior as well as the plant’s effects on the behavior of DBM natural enemies. A series of lab and field experiments were conducted to observe predation and parasitization activity on the L. virginicum compared to cabbage. DBM favored L virginicum relative to cabbage for both feeding and ovipostion. The endoparasitoid, Cotesia plutellae, favored L. virginicum for initial prey searching behavior and more DBM were parasitized on L. virginicum than on cabbage. In conclusion, the putative dead-end trap crops were unsuccessful in preventing the two populations in Hawai`i from completing their lifecycle. However, the naturally occuring weed, L. virginicum, may act as a different type of dead-end trap crop by harboring high numbers of natural enemies of DBM, which could help to control the pest.
Effects of Fiji disease resistant sugarcane varieties on the biology of Perkinsiella saccharicida Kirkaldy
(University of Hawaii at Manoa, 1977) Taniguchi, Glenn Yukio.; Entomology
Fiji disease is a virus disease of sugarcane, Saccharum officinarium L., and some closely related species. At the present time, Fiji disease is confined to Madagascar and the South-West Pacific area. This includes such sugarcane-growing areas as Australia
Deformed Wing Virus (DWV) Transmission Across Pollinators Of Hawai‘i
(University of Hawaii at Manoa, 2020) Santamaria, Jessika; Villalobos, Ethel M.; Entomology
These studies explore the impact Deformed wing virus (DWV) on the pollinators of Hawai‘i. DWV is a well-studied virus, now commonly associated with the European honey bee, Apis mellifera (Hymenoptera: Apidae), populations. The documented decline of honey bee populations worldwide led past researchers to determine this virus played a vital role in their dwindling numbers. Research attention had now shifted to look at the DWV presence in non-Apis communities in the mainland, but only recently has research explored the unique ecology Hawai‘i offers. The first chapter investigates the indirect role of the Varroa destructor mite, a honey bee pest, and how its introduction to the state of Hawai‘i in 2007, influences the continued spread of DWV, not only within honey bee communities, but to surrounding insect populations. In this study, we utilized the limited distribution of the Varroa mite in the Hawaiian archipelago to compare DWV prevalence on non-Apis flower visitors, and test whether Varroa presence is linked to a viral spillover to these populations. We select the two islands: O‘ahu, where V. destructor has been present since 2007, and Maui, where the mite remains absent. Individuals of A. mellifera, Ceratina smaragdula, and Polistes spp. were assessed and used to compare the DWV prevalence in the Hymenoptera community of the two islands. DWV was detected in the non-Apis Hymenoptera collected from O‘ahu but was absent from samples collected on Maui. These results suggest an indirect, but significant, increase on the DWV prevalence in the Hymenoptera community in mite-infected islands. The second study focused on the DWV prevalence in the bee genus, Hylaeus (Hymenoptera: Colletidae). The Hawaiian Islands are home to more than 60 endemic species of Hylaeus, commonly referred to as yellow-faced bees. Their ecological history and distribution are unique to the archipelago and their numbers have unfortunately dwindled in the past years. The decrease in populations have to do with many factors which include destruction of natural habitats, the introduction of predatory wasps, and the introduction of ants to the islands. The introduction of pathogens and diseases has also been suspected but not documented. We sampled populations of two non-native species of Hylaeus, on Oahu, to determine their DWV status. Additionally, DWV strains for these species are reported. For the first time, DWV presence was found for this genus in Hawai‘i. DWV viral levels of combined Hylaeus species were comparable to those of Hymenoptera in previous Hawai‘i studies. However, when divided across the two species, H. albonitens had almost twice the DWV prevalence when compared to H. strenuus. These results may indicate that despite being ecologically and evolutionarily closely related, DWV prevalence can still have great variability within a genus, and DWV strain types vary across non-Apis groups. The third chapter sets a foundation for future DWV research in Hawai‘i, by making a preliminary list of the groups of flower-visiting insects that carry DWV at sites where they overlap with honey bee populations. Pollinators, which rely on flowers as their food source, also encounter a myriad of pathogens when visiting these sites. Yet, determining when and which pathogen a pollinator will encounter during a flower visit is a difficult task. The disease interactions between flower visiting insects is a diverse and complex web, made up of many variables and factors. By mapping these interactions, we can start to better understand the spread of diseases between pollinator communities at these sites, especially when we consider the potential impact DWV may have on these communities. This survey, conducted over a period of 4 years, across various sites on the island of O‘ahu, explores the prevalence of DWV in different flower-visiting insects, and how these viral rates differ over time and across species.
Potential Biological Control Of The Coconut Rhinoceros Beetle On O‘ahu, Hawai‘i
(University of Hawaii at Manoa, 2019) Russo, Mason Harru; Cheng, Zhiqiang; Entomology
Many islands throughout the Pacific have had their palm trees devastated by Oryctes rhinoceros (Coleoptera: Scarabaeidae: Dynastinae), the coconut rhinoceros beetle. O. rhinoceros primarily feeds on coconut palms, Cocos nucifera, but can feed on a variety of other palms and plants of economic value. Integrated pest management is often used to control O. rhinoceros, with a combination of mechanical, cultural, chemical, and biological control methods. O. rhinoceros’s spread across the Pacific was influenced by agriculture, shipping, war, and tropical storms. In 2013 it was detected on the Hawaiian Island of O‘ahu. Due to the regulations associated with bringing in biological control agents to the Hawaiian Islands, a survey was conducted to identify local entomopathogenic fungus strains to test on the O. rhinoceros larvae. Soil samples from around O‘ahu were collected and 73 strains of Beauveria spp. and Metarhizium spp. were tested on lab reared O. rhinoceros first instar larvae. Heterorhabditis indica and Steinernema feltiae entomopathogenic nematodes were collected on O‘ahu for trials as well. O. rhinoceros larvae were reared in the University of Hawai‘i Arthropod Containment Laboratory, with field caught adults brought into the colony weekly. These larvae reflected the field population on O‘ahu, and were used in laboratory assays involving entomopathogenic nematodes and fungi. The entomopathogenic nematode testing did not yield substantial mortality, while the entomopathogenic fungal strains yielded greater than 60% mortality with five prominent strains. Promising entomopathogenic fungi results led to field testing on field caught larvae as well.
Lepidopteran Egg Parasitoid Survey Of O‘ahu: Assessing Parasitism Rates And Parasitoid Diversity In Wild Collected And Sentinel Eggs Across An Elevation Gradient
(University of Hawaii at Manoa, 2019) Logan, Mitchel; Rubinoff, Daniel; Entomology
Egg parasitoids are mostly wasps and flies that oviposit into the eggs of other insects, which are used as a food source for the development of their larvae. They are often purposely employed to control pests in both agricultural and natural settings through the resulting reduction in the populations of targeted pest insects. Hawai‘i is known for its high levels of endemism among insects and plants in particular, but it also has some of the highest numbers of introduced species of arthropods in the world. Many of these introduced arthropods are parasitoids used to control populations of adventive insect pests. Egg parasitoids in particular are often used to target pest populations of Lepidoptera. Egg parasitoids are typically minute insects that are not readily detected during quarantine inspections, or during conventional insect collecting efforts. I summarized the history of egg parasitoid introductions in island systems no greater than 16,637 km2 and surveyed O‘ahu for unrecorded egg parasitoids by using sentinel eggs of three moths: Helicoverpa zea Boddie (Lepidoptera: Noctuidae), Daphnis nerii Linnaeus (Lepidoptera: Sphingidae) and Agrius cingulata Fabricius (Lepidoptera: Sphingidae) and eggs collected from wild populations of Lepidoptera across an elevation gradient on O‘ahu. To assess the effectiveness of sentinel eggs, and to detect egg parasitoid diversity, I also compared parasitism and parasitoid species between wild eggs and deployed sentinel eggs. In total 540 eggs were collected in the wild of which 319 (59.1%) were parasitized and 2,030 sentinel eggs were retrieved of which only 3.1% were parasitized; simple correlation coefficients were taken to compare percent parasitism, proximity to ports, and elevation between wild collected and sentinel eggs. My results reveal that parasitoid species differ by location, and wild collected eggs are parasitized at a higher rate than sentinel eggs, suggesting that such sentinels may not be effective measures of parasitoid impacts or diversity. A negative correlation was found for percent parasitism and proximity to ports in wild collected eggs, and both sentinel and wild collected eggs revealed a mild negative correlation between percent parasitism and elevation with parasitism decreasing at higher elevations. Four parasitoid species were collected in the survey of egg parasitoids on O‘ahu: Ooencyrtus pallidipes (Ashmead) (Hymenoptera: Encyrtidae), Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae), Telenomus sp. and an unidentified Eupelmid.
The Riddle of the Sphinx: Population Ecology of the Endangered Blackburnʻs Sphinx Moth, Manduca blackburni (Lepidoptera: Sphingidae) on an Invasive Host Plant
(University of Hawaii at Manoa, 2019) Elliott, Christine Harrison; Rubinoff, Daniel; Entomology
ABSTRACT Blackburnʻs sphinx moth, Manduca blackburni (Lepidoptera: Sphingidae; Butler 1880), is a large sphinx moth endemic to the Hawaiian Islands. In 2000, it became the second moth and the first Hawaiian insect to be federally listed as an endangered species, yet little was known about its population biology. Its primary host plant is the invasive weed tree tobacco, Nicotiana glauca (Solanaceae). Despite the presence of tree tobacco on six of the seven main Hawaiian Islands, Blackburn’s sphinx moth is currently known from only Maui, Kahoʻolawe, and Hawaiʻi Island where it occurs at densities well below what its invasive host plant would seem to support. In order to facilitate conservation efforts, I set out to analyze changes and patterns in abundance, elucidate ovipositional preferences, and identify the factors responsible for the apparent population suppression of this charismatic Hawaiian moth all on its novel invasive host plant.
Ecological Effects of Solenopsis papuana on Invertebrate Communities in O‘ahu Forests
(University of Hawaii at Manoa, 2018-05) Ogura-Yamada, Cassandra S.; Entomology
The thief ant, Solenopsis papuana, is the most common invasive ant found in upper elevations of mesic forests of Oʻahu, raising concerns about its ecological impacts in these areas. I developed monitoring and control methods to measure and reduce S. papuana densities in experimental field plots, and subsequently assessed invertebrate community responses to this ant suppression six months and one year later, using leaf litter and pitfall sampling methods. Responses in overall community composition, species richness, and abundances of taxa were mixed, but altogether, suggest that S. papuana has broad but relatively weak effects on current ground-dwelling invertebrate communities, which are dominated by nonnative species. Specific taxa, however, may be more vulnerable. Eradication of this ant from the Waiʻanae Mountains is not feasible, but information from this study may help land managers decide whether controlling this ant in small areas to conserve rare and sensitive invertebrate species might be useful.
Management Strategies of New Invasive Insect Pests of Landscape Plants in Hawai‘i
(University of Hawaii at Manoa, 2018-05) Kellar, Matthew K.; Entomology
Landscape plants provide beneficial effects such as increasing air quality, promoting mental health, and improving aesthetics. The need to have effective control methods for pests is important to maintain these benefits. This study investigated manamgent tactics for Oryctes rhinoceros, Josephiella spp., and Paratachardina pseudolobata, pests that attack important landscape plants in Hawaiʻi including coconut palm, Chinese banyan and weeping banyan. Various systemic insecticides were tested on O. rhinoceros in the laboratory. The highest percent of affected beetles were observed in acepahte and imidacloprid treatments. Irrigation did not impose negative impacts on insecticide efficacy and followed similar trends to insecticide treatmetns alone against banyan pests. A comparative study on different systemic application methods on controlling P. pseudolobata found that both injection and soil drench were effective at suppressing P. paratachardina.
Oviposition Behavior of the Female Coconut Rhinoceros Beetle, Oryctes rhinoceros (Coleoptera: Scarabaeidae)
(University of Hawaii at Manoa, 2017-12) Manley, Megan E.; Entomology
The coconut rhinoceros beetle (CRB), Oryctes rhinoceros (L.) (Coleoptera: Scarbaeidae), has become one of the most important coconut and oil palm pests to date. CRB recently emerged in December 2013 as a new invasive pest of coconut palms on O‘ahu, Hawai‘i. Since its detection, efforts have been expended performing delimiting and monitoring surveys, detecting and sanitizing breeding sites, and developing methods for eradication and control. To aid these efforts, information on the factors influencing female adult oviposition behavior and identifying these behaviors is needed. In this study, data and observations were collected from a series of substrate choice tests and depth observations to assess if both lab-‐reared and wild-‐caught CRB have a preference for oviposition site or egg-‐laying pattern. Small or large particle sizes, as well as high (8dS/m) or low (2 dS/m) salinity substrates, were tested and oviposition depths were observed using an observational chamber. Female CRB were found to prefer small particle size substrate and lay their eggs in an aggregated dispersion pattern at various depths up to 119 cm. No preference for substrate salinity was found. Additionally, female CRB were found to differ significantly in their oviposition behavior between lab-‐reared and wild-‐ caught beetle types. These results can help to identify potential breeding sites and can also be implemented into management programs for future eradication and prevention efforts.
Predation and Parasitism of the Kamehameha Butterfly (Vanessa tameamea) on Oahu Island.
(University of Hawaii at Manoa, 2017-08) Maeda, Colby T. L.; Entomology
Hawaii’s official state insect, the Kamehameha butterfly (Vanessa tameamea), is one of only two butterflies native to the Hawaiian Islands. Recently, this iconic butterfly has experienced a population decline and is not present in areas where it once thrived. Since little research has been previously conducted on the butterfly, past studies on other declining Lepidoptera species were examined to gain insight into what factors may be affecting Kamehameha butterfly populations. A rearing methodology for V. tameamea was also developed because sentinel eggs and larvae were needed for field trials, and to provide a basis for future conservation programs. Predation and parasitism rates of V. tameamea were estimated using sentinel eggs and larvae that were deployed for three days under various treatments at four sites on Oahu, Hawaii. Data was analyzed using risk assessment analysis and binomial logistic regression. Bird predation and ant predation varied by site, and parasitism was detected at only one site. In conclusion, results showed that the butterfly could potentially be reintroduced to areas where they are currently extirpated, if certain controls are implemented, and if other factors (such as host plant scarcity or habitat quality) are not limiting.
Effects of Novel "Lights Out" Mulching and Fertilization Turfgrass Renovation Technique on Arthropod, Weed, and Nematode Communities
(University of Hawaii at Manoa, 2017-05) Michalski, Jennifer R.; Entomology
“Lights Out” mulching is a pesticide-free method of weed and pest management that can reduce weed pressure when replanting turf, switching grass types, or completing a total renovation of a designated grassy area. In this two-year study, we addressed the feasibility of using black, geotextile weed mats made of woven polypropylene plastic where: 1) the black plastic mulch significantly reduced light from reaching the soil surface for repeated coverings, 2) a fertilization amendment followed by irrigation on de-thatched ground stimulated weed seed germination to effectively flush the weed seed bank, and 3) prolonged periods of covering eliminated old turf and weed presence before re-establishing new turf. This introduction provides a justification for pursuing this management method, provides a comparison to traditional methods of control, and addresses the gaps in knowledge about Lights Out mulching. A comprehensive literature review is also provided to elaborate on what is known about the effects of plastic mulching on arthropod, weed, and nematode communities.

Browse

Recent Submissions