Browsing by Author "Kring, Timothy Joseph"

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    Biological Studies and Evaluation of Scymnus Coniferarum, a Predator of Hemlock Woolly Adelgid from Western North America
    Darr, Molly Norton (Virginia Tech, 2017-06-07)
    The hemlock woolly adelgid (HWA), Adelges tsugae Annand, is an invasive pest of eastern hemlock, Tsuga canadensis (L.) Carriere and Carolina hemlock Tsuga caroliniana Englem. in the eastern United States. A newly reported beetle predator for HWA, Scymnus (Pullus) coniferarum Crotch (Coleoptera: Cocinellidae) preys on the pest in the western United States, and was approved for release in the eastern United States for the control of HWA. This research investigated the viability of S. coniferarum as a biological control agent of A. tsugae in the eastern United States, as well as the ecological dynamics between S. coniferarum and host prey species in its native range of western North America. In objective one, S. coniferarum predation, reproductive potential, and survival were evaluated in field-cages on adelgid infested T. canadensis in southwestern Virginia. Adult S. coniferarum fed on both generations and all life stages of A. tsugae at rates comparable to other adelgid-specific predators, and survived for extended periods of time in the field. In objective two, host-range tests for S. coniferarum were conducted in a series of no-choice and paired-choice feeding, oviposition, and development studies. Scymnus coniferarum adults fed on all adelgid species, and completed development on HWA and Adelges piceae Ratz. Scymmnus coniferarum oviposition was extremely low. In the final objective, Douglas-fir, Pseudotusga menziesii Mirb., Shore pine, Pinus contorta Dougl., western white pine, Pinus monticola Dougl., and western hemlock, Tsuga heterophylla (Raf.) Sarg. host tree species were sampled in Tacoma, Washington to investigate the life history of S. coniferarum and associated adelgid prey species in the western United States. Scymnus coniferarum adults were found on both pine species, Douglas fir, and western hemlock, and seemed to move between host tree species seasonally. Each host tree supports a different adelgid species, and a limited diet of strictly HWA in host-range tests could have contributed to low oviposition rates. This study suggested that S. coniferarum is a voracious predator of HWA in the field and laboratory. However, S. coniferarum laid very few eggs in laboratory studies, and zero eggs were recovered in field-cage analyses. This suggested that S. coniferarum may rely on multiple adelgid species to reproduce and establish in the eastern United States.
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    Development and Evaluation of Integrated Approaches for Managing of Mexican Bean Beetle, Epilachna varivestis Mulsant
    Nottingham, Louis B. (Virginia Tech, 2017-01-31)
    The Mexican bean beetle, Epilachna varivestis Mulsant, is a major pest of snap beans, Phaseolus vulgaris L. in the Central Appalachian region of the United States. To develop pertinent research objectives, background information on this pest was gathered from literature sources and personal communications with growers, extension agents and other agricultural professionals. In objective one, Mexican bean beetle preference, developmental success and plant injury were compared among three snap bean and three lima bean cultivars in field and greenhouse trials. The cultivar 'Dragon's Tongue' was the most preferred, suitable for development, and prone to injury. Growers may benefit from growing less susceptible cultivars, or by using 'Dragon's Tongue' in trap cropping or push-pull strategies. In objective two, Mexican bean beetle densities, feeding injury, and yield were compared among snap beans grown on metallized plastic (highly reflective), white plastic, black plastic, and bare soil. Metallized plastic provided the greatest level of control, and resulted in the highest yields. Managing Mexican bean beetle by growing beans on metallized plastic may be used as a stand-alone method, or in a push-pull strategy. In the final objective, the effects of snap beans grown from thiamethoxam (a neonicotinoid insecticide)-treated seeds on Mexican bean beetle were assessed in greenhouse and field experiments. Thiamethoxam-treated plants killed 40 to 50% of Mexican bean beetle adults and larvae up to 16 days after planting. In the field, thiamethoxam-treated plants mitigated Mexican bean beetle densities and damage in one out of five experiments, resulting in a yield increase. In none of the five field experiments were differences detected in predatory arthropod species between thiamethoxam and non-insecticide treated beans. In summary, the results of this project suggest that non-chemical management methods, such as cultivar selection and planting beans on reflective mulch, can provide effective control of Mexican bean beetle. Thiamethoxam-treated seed may also provide control of this pest, but only within two to three weeks after planting; otherwise, there is typically no effect on beetles, injury or yield. This doctoral research has laid a foundation for an integrated pest management approach for Mexican bean beetle.
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    Foraging ecology and sampling of Trissolcus japonicus  (Ashmead) (Hymenoptera: Scelionidae) and its host Halyomorpha halys (Stal) (Hemiptera: Pentatomidae) in wild host trees
    Quinn, Nicole Frances (Virginia Tech, 2019-11-27)
    The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive agricultural and nuisance pest in the United States and an increasing number of countries abroad. In the absence of other long-term solutions, biological control presents one of the most promising H. halys management options. An adventive population of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), one of the most effective egg parasitoids of H. halys in their shared native range in Asia, was discovered in the Maryland in 2014 and in Frederick County, VA in 2015. Adventive populations of T. japonicus have also been detected recently in several other states and show strong indications of ongoing range expansion. Despite their importance, the foraging ecology of H. halys and especially of T. japonicus in the USA need further study. Small pyramid traps baited with a low-dose H. halys aggregation pheromone lure and deployed as vertical transects in the canopy of female tree of heaven (Ailanthus altissima (Mill.) Swingle), male tree of heaven, or hackberry (Celtis occidentalis L.), captured significantly more H. halys adults and nymphs near the top of the canopy than at mid- or lower canopy, regardless of host plant. The majority of H. halys egg masses collected via destructive sampling of felled tree of heaven were from mid-canopy, and the majority of those parasitized by T. japonicus were also from mid-canopy, with no T. japonicus emergence from egg masses collected from the lower canopy. A comparison of sentinel H. halys egg masses and yellow sticky traps deployed as vertical transects in tree of heaven revealed that the majority of T. japonicus detections occurred at mid-canopy and that while both methods proved to be equally effective, yellow sticky traps were more efficient for this purpose. This led to the development of a novel T. japonicus sampling method in which a yellow sticky trap is deployed atop a bamboo pole in the mid-canopy of wild host trees. This method was employed to compare the effect of habitat type on T. japonicus captures in female tree of heaven growing in spatially isolated patches, thin windbreaks, and at the edge of contiguous woodlots. Consistent habitat effects on T. japonicus detections were not found between sampling years, but provided the first documentation of the seasonal activity of T. japonicus in the USA. A study of host plant effects on T. japonicus detection in mid-canopy yellow sticky traps did not reveal consistent host plant effects on captures. These data provide important insights into the foraging ecology of H. halys and T. japonicus in the USA, as well as efficient sampling methods for future studies of T. japonicus.
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    Impact of predation by Laricobius nigrinus (Coleoptera: Derodontidae) and Leucotaraxis spp. (Diptera: Chamaemyiidae) on Adelges tsugae (Hemiptera: Adelgidae) and Tsuga canadensis (Pinales: Pinaceae) tree health
    Preston, Carrie E. (Virginia Tech, 2023-12-18)
    The hemlock woolly adelgid (HWA), Adelges tsugae Annand, (Hemiptera: Adelgidae) is an invasive species in the eastern United States and Canada. This scale-like insect feeds on the xylem ray parenchyma cells of eastern hemlock, Tsuga canadensis (L.) Carrière, (Pinales: Pinaceae) and Carolina hemlock, Tsuga caroliniana Englem., resulting in multiple physical and physiological symptoms, all of which commonly leads to tree mortality within 4 to 10 years. Currently, HWA has spread throughout most of the eastern hemlock range and all of the range of Carolina hemlock and threatens the forest ecosystems they serve. In its introduced range, there are no natural enemies specialized to feed on HWA and suppress HWA populations below damaging levels. In the urban environment and at some public locations, the use of chemicals, such as imidacloprid, have been used to temporarily protect hemlocks, however; this does not provide a permanent solution. In the 1990's a classical biological control program for HWA was created with the goal to suppress HWA populations below damaging levels to reduce tree mortality, and to reduce the negative effects associated with the loss of either hemlock species. Presently, four predators have become the main focus of this program: Laricobius nigrinus Fender, Laricobius osakensis Shiyake and Montgomery (Coleoptera: Derodontidae), Leucotaraxis argenticollis (Zetterstedt), and Leucotaraxis piniperda (Malloch) (Diptera: Chamaemyiidae). Throughout the eastern US, La. nigrinus has established populations and expanded its distribution beyond where it has been released. Although it has successfully established and continues to spread, its effect on eastern hemlock health has been unknown. A 1-year study, carried out in 2021, revealed that La. nigrinus predation on the sistens generation not only reduced the sistens generation, but also had a similar net photosynthetic rate to the negative control on 1-2 year old shoot growth. In addition, significantly more shoots were produced for treatment branches with the highest La. nigrinus density. This also led to a significantly reduced aestivating sistens density compared to the no predator treatment. However, predation was insufficient to reduce HWA populations below the suggested damaging threshold of eastern hemlock (< 4 HWA/cm), suggesting that additional predators would be needed. Recently, the western strain of Le. argenticollis had been released in the eastern US. However, its phenology in the eastern US was unknown. A 2-year study, from 2021-2023, revealed that Le. argenticollis eggs and larvae were present when both generations of HWA adults with eggs and HWA nymphs were present. In addition, Le. argenticollis was capable of completing development in NY and VA, showing promise that this species could establish populations in the eastern US. Timing the adult fly releases into cages at the time when sistens were producing eggs resulted in Le. argenticollis phenology to synchronize well with HWA phenology at both locations, thus providing additional support for its release in the eastern US. Another 2-year study conducted in 2021-2022, at five locations (MD, NC, PA, TN, and VA), sought to determine how the predation of La. nigrinus and Le. piniperda, alone and together, would impact the sistens and progrediens generations, as well as how their predation would affect the aestivating sistens density and new shoot growth production. From this study, La. osakensis was found as the dominant Laricobius species present at the TN site, and similarly to La. nigrinus, reduced intact ovisac density in. This provided a small preview in La. osakensis capabilities and how this predator may be impacting HWA populations at locations where it has established. In order to assess Le. piniperda's impact on the progrediens generation, mesh cages were applied to treatment branches at each site. The study found that Le. piniperda could reproduce at all field sites and that the percentage of disturbed progrediens was significantly higher for treatments with Le. piniperda present at all field sites, except at PA in 2022. However, the affect of both of these predators on the aestivating sistens density and eastern hemlock health was inconclusive. In addition, the percentage of new shoot growth was highly variable among treatments at all field sites, and there was no treatment effect on the mean length of new shoot growth produced at all field sites. The results of this study suggests that in order to fully understand the affects of these predators on HWA populations and on hemlock tree health, longer term studies should be conducted. However, this study does provide some insight on the capabilities of these predators in the short term and supports the continued release and redistribution of these predators.
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    Influences of Climate, Competition, and Novel Hosts on Parasitoids of Emerald Ash Borer, and their Establishment in Virginia, and North Carolina
    Ragozzino, Max Louis (Virginia Tech, 2020-07-02)
    Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a species of wood boring beetle which feeds on the inner bark of ash trees, Fraxinus spp., and white fringe tree, Chionanthus virginicus L. In North America emerald ash borer feeding damages the trees vascular system, killing the tree in 1-6 years after initial infestation. Emerald ash borer's native range is north east China, the Russian Far East, and the Korean peninsula. In the mid-1990s emerald ash borer was accidentally introduced to Michigan from the Hebei and Tianjin city province regions of China. Since then, due to human-aided transport and natural spread, emerald ash borer now infests 35 states and five Canadian provinces. Studies in to Asia discovered several species of parasitic wasps which feed and reproduce on emerald ash borer; four of these species were approved for release in the United States. Three species which attack emerald ash borer larvae Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), Spathius agrili Yang (Hymenoptera: Braconidae), and Spathius galinae Belokobylskij and Strazanac (Hymenoptera: Braconidae), and one species which utilizes emerald ash borer eggs, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae). This research focuses on the control of emerald ash borer using the three larvae-utilizing species of parasitic wasp. The first objective of this research focuses on the synchrony of emerald ash borer larvae with the early spring emergence of S. agrili and S. galinae. The first objective also assessed how two different cold temperature treatments changed the emergence timing, and health of the wasps. The second objective assessed to determine the effects of competition between S. agrili and S. galinae when they were exposed to a single emerald ash borer larvae sequentially, and simultaneously. When exposed sequentially, the first wasp held the competitive advantage, but when exposed simultaneously S. agrili had a small advantage, but did not completely exclude S. galinae. The third objective focused on the potential for two larval parasitoids, S. agrili and S. galinae to parasitize emerald ash borer larvae in the novel host plant white fringe tree. We determined that both parasitoids are capable of finding and parasitizing emerald ash borer larvae within a non-ash host. Finally, we located 13 stands of emerald ash borer infested ash in Virginia and North Carolina in order to determine its life cycle, and overwintering life stage. We determined that emerald ash borer overwinters at different life stages, and has a more complex life cycle than previously reported. Additionally, all three species of larvae-utilizing parasitic wasp were recovered at field sites at least 1 year after release. These results all show promise for the biocontrol program, and indicate that biocontrol of emerald ash borer could be successful in Virginia and North Carolina.
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    Laboratory rearing, establishment, subterranean survivorship, and thermal requirements of Laricobius spp. (Coleoptera: Derodontidae), biological control agents released for Adelges tsugae (Hemiptera: Adelgidae)
    Foley IV, Jeremiah Robert (Virginia Tech, 2021-10-29)
    The hemlock woolly adelgid (HWA) (Adelges tsugae [Annand]) (Hemiptera: Adelgidae) is a non-native lethal pest to eastern hemlock (Tsuga canadensis [L.] (Pinales: Pinaceae), and Carolina hemlock (Tsuga caroliniana [Engelmann]) (Pinales: Pinaceae). In the early 2000's, a robust biological control initiative using Laricobius spp. (Insecta: Coleoptera) was launched with the goal of decreasing HWA's impact to hemlock and the associated ecosystems on landscape level. Since then, two Laricobius agents, Laricobius nigrinus Fender (Coleoptera: Derodontidae) and Laricobius osakensis Montgomery and Shiyake (Coleoptera: Derodontidae) have been evaluated, approved, and released. The production and subsequent release of these agents has largely occurred through mass rearing efforts by Virginia Tech. A descriptive analysis of these rearing and release data over the past 16 years at Virginia Tech revealed that the mass production of these agents has been consistently limited by: 1) excessively high rates of subterranean mortality and 2) early subterranean emergence. Very little is known about the subterranean life cycle of these species in the field in terms of survivorship and timing of emergence. Additionally, the thermal limits and rates of development are unknown for L. osakensis and were thus further investigated. In 2019, surveys within the urban environment in two counties in southwest Virginia were conducted to determine if these agents have dispersed from their original release location. Laricobius nigrinus was documented to have established outside of release sites in 100 and 75% of the surveyed grids containing HWA infested hemlocks. The establishments of these species in easily accessible locations allowed for the use of field-caught larvae, in addition to laboratory-produced larvae, for experiments. Experiments were conducted in 2019-2020 to determine the overall subterranean survivorship in relation to site condition, differences in survivorship between field-caught vs. laboratory-reared, and the seasonal timing of emergence. We found that the average field subterranean survivorship (17.1 ± 0.4%) was significantly less than the historical production of these agents in the laboratory (37.5 ± 13.6%). We found that as soil pH and organic matter depth increased, survivorship decreased. While the majority of emergence occurred as expected in the fall, a surprising amount of emergence also occurred in spring and summer. The rate of development and the minimum threshold temperature for each life stage were determined through constant temperature experiments, and were used in the construction of a phenological forecast model. Laricobius osakensis minimum threshold temperature (3.6°) from egg to adult was similar to that of other Laricobius spp., but completed development at higher a constant temperature (22°C). Our results suggest L. osakensis can handle the same colder climates as L. nigrinus, but may be better adapted for warmer locations than L. nigrinus. Laboratory rearing, establishment, subterranean survivorship, and thermal requirements of Laricobius spp. (Coleoptera: Derodontidae), biological control agents released for Adelges tsugae (Hemiptera: Adelgidae)
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    Post-release establishment and supercooling point assessment of Laricobius osakensis, a predator of the hemlock woolly adelgid
    Toland, Ashley Anne (Virginia Tech, 2018-03-29)
    The hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae), is an invasive pest from Japan that is causing significant hemlock mortality in the eastern U.S. The most promising control method is biological control. Beetles in the genus Laricobius are adelgid specialists. In 2005, Laricobius osakensis, was discovered in Japan and in 2010 was approved for release in the eastern United States and there have now been more than 60 releases. In 2014, the polar vortex resulted in significant HWA mortality in the eastern U.S., depleting the food source for L. osakensis, which resulted in low field recoveries of them. In the 2015-2016 field season, there were 14 larvae recovered from the field, and the 2016-2017 field season yielded 90 larvae. A significant correlation was found between Laricobius beetles recovered and HWA density, between HWA density and plant hardiness zone, and a negative correlation between Laricobius beetles recovered and average tree health. Understanding more about the supercooling point of L. osakensis gave insight to its ability to survive subfreezing temperatures as occurred in 2014. Comparison of the supercooling point between the northern and southern populations of L. osakensis, and to the other released HWA predator, L. nigrinus, will allow us to determine which biological control agent is best suited for release in the coldest regions. The overall mean supercooling points of northern L. osakensis was -13.52 oC, southern L. osakensis was -13.42 oC, and L. nigrinus was -13.57 oC. There were no significant differences between species or populations.
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    Understanding Japanese Maple Scale Biology to Inform Sustainable Pest Management Practices in Virginia Nurseries
    Wyatt, Mollie McDonnell (Virginia Tech, 2024-06-04)
    Lopholeucaspis japonica (Cockerell) (Hemiptera: Diaspididae), commonly known as Japanese maple scale (JMS), is an invasive pest established in the United States in 1914. Over the past decade, JMS infestations have escalated, posing a significant threat to the nursery industry, and resulting in economic losses from unsellable infested plants. The limited understanding of JMS hampers the development of effective management strategies, intensifying the financial impact of this destructive pest. To contribute to the development of a sustainable pest management program, it is crucial to acquire knowledge of JMS's natural history, biology, and dispersal capabilities. Management costs can be reduced by determining the optimal timing for scouting and spraying through peak crawler emergence and the identification of overwintering life stages. Understanding JMS dispersal patterns within tree canopies can lead to the refinement of scouting methods, such as strategically placing the tape method (for monitoring crawlers). A two-year study took place at two separate locations and on boxwoods (2022-2023) and red maples (2023). Our phenology findings indicated that there were two generations and prolonged crawler presence which can extend over a period of 34 weeks (March-October) during the growing season. The first generation of crawler emergence on boxwoods started as early as the second week of March [110-114 Growing Degree Days in base 50°F (GDD50)], with the first peak occurring in mid-June [1179-1514 GDD50]. The second generation depending on the year began in July and peaked between early September and mid-August due to overlapping from prolonged presence of crawlers. Crawler emergence on maples indicated the first peak during the second week of July, followed by the second peak during the third week of August. Management practices, including monitoring and chemical control and based on phenology data, could be suggested to begin early March and continue throughout the season putting high pressure on crawlers during the peaks of activity. Overwintering studies from this project suggested JMS could be developing throughout winter with immatures found in January and February while in March the highest population was adults. Using horticultural oil during the winter months may help with JMS infestations. To investigate dispersal patterns, the canopy of experimental plants of maples and boxwoods were divided into top, middle, and bottom sections based on plant height. Comparative analysis of JMS crawler densities within the canopies of maples indicated that the middle canopy sections exhibited higher crawler densities compared to the top sections. However, when evaluating all three sections (top, middle, and bottom), the bottom sections displayed the highest crawler densities. Examination of cardinal points within the top and middle canopies of maples revealed a widespread distribution pattern. In contrast, no significant differences in crawler densities were observed between the various canopy sections of boxwoods, indicating a uniform distribution across the plant.