Rainfastness of insecticides is an understudied aspect of agricultural research. Little is known about the residual of commonly used products for key pests of cotton, as well as their residual after a rainfall event. This project was designed to evaluate the impact of rainfall on the performance of commonly used insecticides for tobacco thrips, Frankliniella fusca (Hinds); tarnished plant bug, Lygus lineolaris (Palisot de Beauvois); and bollworm, Helicoverpa zea (Boddie), management in cotton. Laboratory and field experiments suggest that rainfall occurring within 16 hours after application had a negative impact on the performance of most insecticides. Chemical analyses of leaf tissue using a mass spectrometer confirmed what was observed with field and laboratory experiments. Although direct comparisons between insecticides cannot be made, results from this study suggest that spinosyns and insect growth regulators appeared to have the longest residual after a rainfall event.

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Cotton (Gossypium hirsutum L.), is cultivated in the United States, primarily in regions characterized by long, hot summers to optimize plant growth. Virginia is the northernmost state where cotton is grown, with approximately 84,000 acres annually. The unique challenges of cultivating cotton in Virginia stems from its relatively short season due to its geographical location, lack of large contiguous acreage, and distinctive issues with pests. A significant pest of this region is the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), which emerged as a major threat to mid-Atlantic cotton during the late 2010s. L. lineolaris utilize a variety of wild and cultivated hosts to survive the winter months. The overwintering success and distribution of diapause survival L. lineolaris was measured on cover crops and weeds common in the Mid-Atlantic. Densities varied between weed and cultivated hosts, with L. lineolaris exhibiting increased survival in legumes compared to grains. Carbohydrate, lipid and protein levels were measured within diapausing and non-diapausing L. lineolaris specimens. Overwintering specimens usually had elevated level of carbohydrates and lipids, while containing decreased concentrations of protein. Nutrient quantification provided an effective tool in selecting for diapause status in L. lineolaris. Through the results from this study, an alternative method to dissection for determining diapause status in L. lineolaris has been identified. In the spring, movement of L. lineolaris throughout the landscape is highly dependent on host senesce. Flight analysis, behavioral assays and nutritional quantification assays on L. lineolaris populations from different weed hosts were performed to assess the flight capacity of specimens fed from different hosts. While weed hosts type provided populations with differing internal nutrient levels, sustained flight was not different between populations. When dispersal of L. lineolaris into cotton occurs, insecticide treatments following scouting are often necessary to prevent economic damage to the plant. Insecticide experiments were conducted aiming to assess the impact of different active ingredients on L. lineolaris, secondary pests, and natural enemy populations. Findings indicated that insecticides used to control L. lineolaris were successful at lowering pest populations and acephate was found to impact natural enemy populations. Plots applied with acephate experienced secondary pest outbreaks, highlighting the crucial role of natural enemies. / Doctor of Philosophy / Cotton is cultivated throughout the southern United States, extending up the east coast and into North Carolina and Virginia. Virginia poses unique challenges for cotton growers due to specific pest issues and need for region-specific research. The tarnished plant bug is a key pest of mid-summer cotton across this region. Overwintering studies were conducted to investigate host preferences on cover crop and weed hosts, as well as diapause survival and termination timing on cover crops. These studies revealed that hairy vetch and deadnettle species may harbor larger populations compared to other weed hosts, and that cover crops such as hairy vetch and crimson clove led to greater overwintering survival compared to grains. During diapause, metabolic changes occur that can lead to increased fat body to aid in overwintering survival. Diapausing and non-diapausing tarnished plant bugs were used in assays to quantify differences in the nutrients commonly found in this fat body. This study successfully found differences in carbohydrates, lipids and proteins levels between the diapausing and non-diapausing populations. This may allow for the identification of reproductive status of tarnished plant bugs based on nutrient levels. Flight capacity, activity levels and nutrient levels in tarnished plant bug populations taken from spring and summer weed hosts were investigated, with the objective to understand the ability of these populations to transition to cotton in the mid-summer. There were some indicators that flight initiation may be influenced by weed host, while all populations had similar flight potentials. Once in cotton, tarnished plant bugs are primarily treated with chemical insecticides which may produce unknown consequences to the system as a whole. Experiments were conducted to assess the impact of insecticides on non-target species within cotton were conducted in the field. Certain insecticides were identified to be harmful to non-target and potentially beneficial insect species, which contributed to outbreaks of other secondary pest species.

The squash bug, Anasa tristis De Geer (Hemiptera: Coreidae), is a serious pest of cucurbit crops across the US, especially within summer squash (Cucurbita pepo L.) systems. Using its piercing sucking mouthparts, squash bug feeds on both leaf tissue and fruits, potentially leading to leaf necrosis, seedling death, and yield loss. Currently, A. tristis management strategies in summer squash focus exclusively on insecticide applications. Given that continuous use of insecticides imposes negative side effects on many non-target species, the major objective of this dissertation was to identify new and understudied management strategies for minimizing A. tristis damage in Virginia summer squash. To accomplish this goal, we first performed experiments to test the effects of colored mulches on squash bug density. A two-year field replicated study conducted in 2019 and 2020 in southwest Virginia found that black, white, and reflective plastic mulch colors had no effect on squash bug adult, egg mass, or nymphal densities. Overall, we observed a broad plastic mulch effect, as summer squash plants grown in any plastic mulch color tended to harbor greater densities of squash bug life stages than plants grown on bare ground. Next, the potential of augmentative releases of egg parasitoid, Hadronotus pennsylvanicus Ashmead (Hymenoptera: Scelionidae) was assessed by deploying lab-reared parasitoids on organic farms growing summer squash in southeastern Virginia in 2020 and 2021. In both years, we found higher levels of A. tristis egg parasitism at H. pennsylvanicus release sites compared to sites where the parasitoids were not released. Further, higher egg parasitism at the release sites was observed within two weeks of the field deployment date. The third goal of this dissertation research was to characterize the relationship between squash bug life stages and marketable summer squash yield. In 2020 and 2021, summer squash fields were established in Whitethorne, Virginia and individual plants were labeled as either 'managed' or 'infested'. Managed plants were subject to weekly manual removal of all squash bug egg masses and nymphs, while infested plants were left to have natural densities of squash bug life stages. We performed weekly A. tristis surveys on all infested plants in both years and added H. pennsylvanicus surveys on infested and managed plants in 2021. Also, we collected all fruit produced by each plant. Managed plants were found to produce more marketable fruit and fewer squash bug-damaged fruit than infested plants. Linear regression analyses of initial two-week accumulated squash bug life stage counts displayed adult and nymph densities to be significantly associated with marketable fruit yield per plant. However, nymphs showed a considerably stronger relationship with marketable yield than did adults. Hadronotus pennsylvanicus was visually sampled during each of the eight sampling weeks, but did not exhibit high egg parasitism until the latter half of the sampling interval. Lastly, we evaluated the toxicity of reduced risk insecticides on A. tristis nymphs and H. pennsylvanicus adults. To do so, we conducted laboratory bioassays exposing nymphs to insecticide treated summer squash fruit and parasitoids to treated filter paper, and recorded mortality at 24, 48, and 72 h following initial exposure. Only one reduced risk insecticide, flupyradifurone, was found to be highly toxic to squash bug nymphs and nontoxic to the parasitoids. Overall, the results of these studies will offer much needed information to improve the success and sustainability of squash bug management programs, as well as provide a fundamental basis and spark motivation for future research in squash bug biological control. / Doctor of Philosophy / The squash bug is a serious insect pest of summer squash across the United States. Squash bugs inflict damage by feeding on plant leaves, stems, and fruits, leading to significant reductions in fruit yield and overall economic losses for growers. To date, farmers have few useful tools to minimize squash bug damage in their summer squash crop, and resort to over-applying insecticides. While this use of insecticides helps lower squash bug numbers, it often has negative side effects on the environment and important beneficial insect species like pollinators. To better understand the squash bug as a summer squash pest and to promote nonchemical ways to reduce squash bug damage, this dissertation research pursued answers to questions regarding: (1) the effect of plastic mulch color on squash bug numbers, (2) the use of squash bug natural enemies to control squash bugs, (3) the relationship between numbers of squash bugs and damaged summer squash fruits, and (4) whether new types of insecticides can control squash bugs and also be safe for beneficial insects. The results of this research will provide new insights on current issues with squash bug pest management. In particular, this work will provide summer squash farmers with useful knowledge that can be applied to their future efforts to responsibly control squash bugs in their fields and maximize their crop yields. With more research-supported and sustainable squash bug control tools, farmers will be able to not only adopt more environmentally-friendly food production practices, but also lower their overhead farm management costs and ultimately provide higher quality squash to consumers.

Edamame (Glycine max (L.) Merr.), also known as vegetable soybean, is primarily grown and consumed in Asia. In recent years, the demand for edamame in the United States has risen due to its health benefits as an alternative, plant-based protein. Due to the lack of domestic production, most edamame is imported from Asia. In an attempt to increase domestic production, research efforts have begun in Virginia and other regions to develop cultivars and best management practices for growing edamame in the mid-Atlantic region. Beginning in 2018, edamame trials examining breeding lines and cultivars were conducted to look at their suitability for this region. These varieties were sampled and evaluated for insect and disease complexes as well as their implications on plant yield and quality. Most of the insects and diseases that were found were very similar to pest complexes commonly found in cultivated soybeans in Virginia. However, due to edamame being marketed as a vegetable, insects and diseases that caused unsightly blemishes or damage to the pods or seeds were most concerning. Multiple insects and diseases were present but some of the most important insects and diseases we observed from 2018-2020 were pod feeding stink bug (Hemiptera: Pentatomidae), as well as the diseases like purple seed stain, Cercospora kikuchii, and bacterial pustule, Xanthomonas axonopodis pv. glycines. From 2019-2021 an integrated pest management study was conducted to determine best management practices for minimizing insecticide applications while applying them at thresholds to control key pests. In three growing seasons, I was able to determine that pesticides can be limited prior to flowering while insecticide inputs will need to be increased after flowering to protect the pods from pests, specifically stink bugs. Additionally, from 2019-2021 insecticide and fungicide field trials were conducted to test different pesticides on their efficacy against pod damaging pests and diseases. The growing seasons between 2019 and 2021 resulted in varying insect and disease pressure that led to inconsistent results. However, insecticides such as cyclaniliprole and sulfoxaflor performed well compared to other treatments. Lastly in 2020-2021, corn earworm (Helicoverpa zea [Boddie], Lepidoptera: Noctuidae), an important soybean pest and most likely a major pest of edamame, was tested for pyrethroid susceptibility and resistance across the state using a bean-dip bioassay. Pyrethroid efficacy to control this pest across Virginia seemed to vary by location and year, however, the bean-dip bioassay proved to be a time-efficient strategy for further monitoring these populations in the coming years. / Doctor of Philosophy / Edamame, also known as vegetable soybean, is primarily grown and consumed in Asia. Due to the lack of domestic production, most edamame is imported from overseas. Edamame trials were conducted in Virginia beginning in 2018, to look at production practices suitable for growing this crop in the region. Scientists observed edamame to document insect and disease complexes as well as their implications on yield and quality. Most of the insects and diseases that were found were very similar to what is known to already occur in soybeans. However, due to edamame being marketed as a vegetable, insects and diseases that left blemishes or damage to the pod were most concerning. Multiple insects and disease were present but some of the most important insects and diseases we observed were pod feeding stink bug species as well as the diseases purple seed stain and bacterial pustule. In 2019-2021 a pest management study was conducted to determine best management practices for minimizing insecticide applications while applying them at thresholds to control key pests. We were able to determine that pesticide usage can be limited prior to flowering while they will need to be increased after flowering to protect the pods. Additionally, in 2019-2021 insecticide and fungicide field trials were conducted to determine the efficacy of materials against pod damaging pests and diseases. The growing seasons between 2019 and 2021 resulted in varying insect and disease pressure, however, several insecticides with reduced ecological impacts out preformed others. Lastly in 2020-2021, corn earworm, a major pest of soybean and presumable of edamame, was tested for pyrethroid susceptibility and resistance across the state using a bean-dip bioassay. Pyrethroid efficacy across Virginia seemed to vary by location and year but the bean dip bioassay method proved to be a time-effective strategy for monitoring the states corn earworm populations against insecticides.

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. / Doctor of Philosophy / The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive agricultural and nuisance pest from Asia that is widely distributed in the United States and is present in an increasing number of countries abroad. In the absence of other long-term management solutions, biological control via the actions of natural enemies presents a promising brown marmorated stink bug management option. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), also known as the samurai wasp, is one of the most effective egg parasitoids of brown marmorated stink bug in Asia. Samurai wasp arrived in the USA without deliberate introduction and was first detected in Maryland in 2014 and subsequently in Frederick County, VA in 2015. It has continued to expand its range in the USA and was recently detected in several eastern and western states. Despite their importance, little is known of where brown marmorated stink bug eggs, nymphs, and adults are most likely to be found in wild trees. Even less is known about where samurai wasp is likely to occur within its new range. To address these issues, traps containing a lure to attract brown marmorated stink bug were placed in the upper, middle, and lower canopy of female tree of heaven (Ailanthus altissima (Mill.) Swingle), male tree of heaven, and hackberry (Celtis occidentalis L.). Significantly more brown marmorated stink bug adults and nymphs were caught in traps near the top of trees than in those at other canopy locations, with no effect of host plant species observed. The majority of brown marmorated stink bug egg masses collected from felled tree of heaven were from the middle of the canopy. The majority of samurai wasps emerged from egg masses collected from the mid-canopy, while none emerged from those collected from the lower canopy. In a comparison of sentinel brown marmorated stink bug egg masses and yellow sticky traps placed in the upper, middle, and lower canopy of tree of heaven, the majority of samurai wasp detections occurred at mid-canopy. Both methods were found to be effective, but yellow sticky traps required less time and effort to use. This led to the development of a new sampling method for samurai wasp, in which a yellow sticky trap was deployed atop a bamboo pole in the mid-canopy of wild host trees. Using this technique, the effect of habitat type on samurai wasp captures was examined, revealing no consistent effects on detections. However, this study provided the first documentation of when samurai wasps are present and most abundant during the spring and summer. A study of host plant effects on samurai wasp captures, also using yellow sticky traps placed in the mid-canopy of trees, did not reveal consistent host plant effects on captures. These data provide important insights into the interactions of brown marmorated stink bug, samurai wasp, and their environment in the Mid-Atlantic region of the USA, as well as an efficient tool with which to study the samurai wasp.

Programmers often have to spend a significant amount of time inspecting the software code and execution traces to identify the root cause of a software bug. For a multithreaded program, debugging is even more challenging due to the subtle interactions between concurrent threads and the often astronomical number of possible interleavings. In this work, we propose a logical constraint-based symbolic analysis method to aid in the diagnosis of concurrency bugs and find their root causes, which can be later used to recommend repairs. In our method, the diagnosis process is formulated as a set of constraint solving problems. By leveraging the power of constraint satisfiability (SAT) solvers and a bounded model checker, we perform a semantic analysis of the sequential computation as well as the thread interactions. The analysis is ideally suited for handling software with small to medium code size but complex concurrency control, such as device drivers, synchronization protocols, and concurrent data structures. We have implemented our method in a software tool and demonstrated its effectiveness in diagnosing subtle concurrency bugs in multithreaded C programs. / Master of Science

The stink bugs, (Pentatomidae) harlequin bug (Murgantia histrionica), brown marmorated stink bug (Halyomorpha halys), and southern green stink bug (Nezara viridula) are significant agricultural pests both in the United States and globally. The aggregation or sex pheromones produced by these insects are known to be bisabolene-type sesquiterpenoids; however, the biosynthetic pathways in the formation of these pheromones are unknown. Here we provide evidence that Pentatomidae produce sesquiterpene aggregation pheromones de novo and discuss the evolution of terpene biosynthesis in stink bugs. According to transcriptome analyses, the investigated stink bug species express at least two isoprenyl diphosphate synthases (IDSs), one of which makes (E,E)-farnesyl diphosphate (FPP) as the general precursor in sesquiterpene synthesis, whereas other IDS-type proteins function as terpene synthases (TPSs) generating intermediates in sesquiterpene pheromone formation. The TPS genes are expressed in a sex- and tissue-specific manner. Based on phylogenetic analysis, these IDS-type TPSs arose from trans-IDS progenitors in divergence from bona fide IDS proteins. Compared to microbes and plants, the evolution of TPS function from IDS progenitors in insects appears to have occurred more recently. The discovery of TPS genes in stink bugs provides valuable insight into pentatomid and insect terpene biosynthesis. Moreover, the identified genes may be used in developing alternative management strategies for stink bug pests. / PHD