Entomology

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Research from the Department of Entomology. The department is part of the School of Natural Resources, and their website may be found at https://www.ndsu.edu/snrs/

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Aphid Interactions with Environmental Variation in the Field and Lab
(North Dakota State University, 2015) McLean, Erin Leigh
A basic tenet of ecology is that organisms are affected by both abiotic factors and other organisms; therefore, there is value in understanding interactions in our changing world. Aphids are model organisms for questions regarding many interactions. I explored three aphid-centered studies. (1) Rearing aphids in a certain temperature changed their response to exposure to different temperatures. Short term exposure to warmer temperatures increased fecundity, but being raised in higher temperatures lowered fecundity across treatments. (2) Feeding on aphids by lady beetles in the lab was measured after exposure to varying temperatures with or without prey. Warming without prey was detrimental, but warming while continually fed invoked more predation than the cooler temperature. (3) Soybean aphids, natural enemies, and other pests vary in space and time. We surveyed soybean to explore the effect of field locations, management, and year on arthropod community structure and found a predominant year effect.
Behaviors Mediate Aphid Interactions with Natural Enemies and the Environment
(North Dakota State University, 2016) Kopco, James
Behavior is a crucial component of ecology that mediates how animals interact with one another and with the environment. Behaviors can allow animals to avoid the harmful effects of things like competition, predation, and extreme abiotic conditions. However, animals often have constraints that limit the potential benefits of their behaviors, so we addressed what factors contribute to these constraints in plant-aphid-wasp systems. Parasitoids of aphids are tiny wasps that lay their eggs in aphids, where the larva feeds and develops. Each aphid can only sustain a single parasitoid, so parasitoids mark aphids when they lay an egg to discourage others from laying additional eggs. Not all parasitoids mark aphids the same way, and whether species with different marks can recognize one another’s mark was unclear. We found that parasitoids with different marks fail to respond to one another’s marks. Because these parasitoids laid eggs in aphids that were already parasitized, competition between them will occur through mortal combat between the larvae rather than egg-laying restraint in the adults. Parasitoid attack induces aphid behaviors such as fighting, running away, or dropping off the host plant. These behaviors can deter or evade the attacker, but they cost the aphid an opportunity to feed. This feeding interruption decreases the number of offspring the aphids produce. When aphids run from a threat, they usually resettle on the newest leaves of a plant, where their reproduction is enhanced. However, when they drop from a plant to escape, they resettle randomly and do not benefit from the better location, indicating that more vigorous responses can lose benefits. We also showed that aphids exhibit similar movement and resettling behaviors when disturbed by heat shocks. However, this behavior did not affect aphid reproduction or survival when induced by a heat shock. While movement to new leaves appears to be a general response to several disturbances, its benefits to aphids only occur in specific situations. We have shown that behaviors can be constrained by unfamiliar stimuli and the general context in which they are invoked. These constraints can dictate how insects interact with each other and the environment.
Collection and Analysis of Volatiles of Various Cultivated Sunflower, Helianthus Annuus, (Asteraceae) Germplasm and Investigation of Some Aspects of Host Selection in Adult Red Sunflower Seed Weevil, Smicronyx Fulvus L., (Coleoptera Curculionidae)
(North Dakota State University, 2017) Lokumana, Charithra Rathnamali
Plants of sunflower germplasm putatively resistant or susceptible to the red sunflower seed weevil, Smicronyx fulvus (Coleoptera: Curculionidae) were used to test the hypothesis that the volatile composition of these two types are different and may influence acceptance/rejection of sunflower germpalsm by S. fulvus. At least 13 volatile terpenoids were released by the different plant lines, with some varying in concentration according to plant line, head maturity, and time of day. Comparison between resistant and susceptible plant lines showed differences in concentrations of less abundant compounds (3E)-4,8-dimethyl-1-3-7-nonatriene, α-copaene, bornyl acetate, β-elemene, β-selinene and germacrene-D, indicating that, one or more of these compounds may be useful markers for resistance/susceptibility to S. fulvus. In behavioral binary choice bioassays, S. fulvus adults were attracted to sunflower heads, preferring R5.5 over R4 and R6 heads, and susceptible to resistant plants. Video recordings indicated both volatile and contact chemicals may be involved in host acceptance/rejection.
Conspectus of Aeptini Stål, 1871 (Hemiptera: Heteroptera: Pentatomidae: Pentatominae)
(North Dakota State University, 2017) Faúndez, Eduardo I
The Pentatominae tribe Aeptini is revised. A key to the known genera is provided, together with redescription and figures. The genus Paramenestheus is revised, including a key to the species and figures to all the included taxa. Two new genera and eight new species are discovered and described. A phylogenetic analysis is included for the Aeptini, with two approaches, cladistic and maximum likelihood, both morphologically based. After these analysis it is concluded that it is a monophyletic tribe and has to be split into two subtribes: Aeptina (including Aeptus and Eribotes) and Menesthina (including Aeliosoma, Hillieria, Menestheus, Paramenestheus, Pseudaelia, New Genus 1, New Genus 2.). Diagnoses for both subtribes are included. Biogeographically it is hypothesized that the Aeptini have a Gondwanian origin which explains it current disjunct distribution in Africa and Australia. The importance of the findings on this dissertation, as well as the relationships among Aeptini and other Pentatominae groups is commented and disccused. Special reference is made to the importance of the presence of a mesosternal sulcus as a major character that may lead to a reclassification of the Pentatominae, having the Aeptini as one of the basal groups. After all the changes proposed on this dissertation the Aeptini is now comprised of two subtribes, nine genera and 30 species.
Crop and Prairie Grasses Serving as Hosts for the Hessian Fly
(North Dakota State University, 2012) Li, Yue
Insect herbivores typically parasitize a relatively small number of plant species. Host specialization is presumed to be a result of evolutionary arms races, with insect adaptations ultimately restricting host range. Being a gall-maker, the Hessian fly has highly evolved interactions with plant hosts. As a consequence, its host range is expected to be narrow. Two crop species, wheat and barley are hosts of the Hessian fly. I studied whether non-crop grasses can also serve as hosts. Included in tests were seven grass species that are important components of the grasslands of the Northern Great Plains. Although less suitable than wheat and barley, all seven species received eggs and five of the seven species supported development of offspring to the adult reproductive stage. Results indicate a broader host range than was expected. A benefit of being able to use non-crop grasses is availability of alternate hosts when superior crop hosts are not available.
Density and Movement of Soybean Aphid, Aphis Glycines (Hemiptra: Aphididae) in Response to Temperature and Resistant Soybean Plants
(North Dakota State University, 2012) Whalen, Rebecca Ann
Movement is one way herbivores respond to their host plant, yet the movement of relatively immobile insects has received little attention. We studied how the movement and density of apterous soybean aphids responds to a resistant soybean variety and different temperatures. In Chapter One, we examined aphid movement both within and between soybean plants that varied in their resistance to aphids. Aphids on resistant plants had a wider dispersal, apparently due to greater aphid movement. Consequently, aphids on resistant plants could move to neighboring susceptible plants, thereby increasing their density. In Chapter Two, we measured aphid density and dispersal on resistant and susceptible plants when insects and plants were exposed to two different temperatures. Here, movement behavior was affected by both plant resistance and temperature. Moreover, temperature and plant resistance interacted to influence aphid density. Our results indicate the important role that movement can play in an herbivore's response to plant resistance.
Effect of Larval Diet on Endogenous Carbon Reproductive Resources of Fifth Instars and Adult Females of the Moth, Heliothis Virescens
(North Dakota State University, 2013) Suman, Smita Dutta
Mostly adult Lepidoptera feed on plant nectar. That is, adults can only contribute to carbon, and not nitrogen, acquisition. The moth Heliothis virescens were used to explore the hypothesis that larval nutrition influences various adult carbon pools and that these, in turn, may affect pheromone production quantitatively. H. virescens larvae were reared on diets differing in carbohydrate, fat or protein content and resulting 5 th instars and adults were analyzed for carbon pools, hemolymph trehalose concentration (HTC) and lipid content. Across all the diet treatments, changes in carbohydrate content affected carbon pool the most. In particular, for insects reared on a high carbohydrate diet, adults had a greater lipid content, while for insects reared on a low carbohydrate diet, adults had a lower HTC, compared to insects reared on the control or other diets. By contrast, changes in protein and fat had little effect on HTC and lipid content of adults.
The Effects of Abiotic Climate Change Factors on Aphid Life History and Populations
(North Dakota State University, 2015) Alfonso, Joseph Vincent
While the effects of many abiotic factors associated with climate change have not been extensively studied, work on model organisms is beginning to help predict effects on similar species. Research on climate change has been dominated by temperature effects on organisms, but additional factors are being studied, including changes in atmospheric CO2 concentrations, wind patterns, precipitation patterns, ultra-violet (UV) radiation, night-time temperatures, and daily high temperatures (heat shocks). We review these effects on aphids and present experimental findings on the effects of night-time warming on pea aphid population growth and birth rates. Aphid populations changed when warmed at different times of a day (overnight vs. during the day), but changes to individual aphid birth rate were not responsible for the population level pattern. Although the exact mechanism is still unclear, increasing nightly temperatures matters for pea aphid population growth and could influence interactions with other species.
The Effects of Salinity on Herbivorous Pests of Corn and Soybean
(North Dakota State University, 2016) Eichele, Jaclyn Lee
Many environmental factors, including soil characteristics, are critically important for plants, herbivorous arthropods, and their interactions. Despite increasing evidence that soil salinity can drastically impact plants, little is known about how salinity affects the herbivorous arthropod pests feeding on those plants we investigated how soil salinity affects two major crop pests: the two spotted spider mite (Tetranychus urticae) feeding on corn and soybean and the soybean aphid (Aphis glycines) on soybean. We quantified the impact of salinity by measuring demographic characteristics and behavior of pests on plants grown in soil with various levels of salinity. Overall, both crop pests performed better as salinity increased. These studies suggest that salinity can be just as important for herbivores as it is for plants. Moreover, the negative effects of soil salinity on crop plants in agroecosystems may be further compounded by a greater risk of pest problems.
Effects of Soybean Aphid Resistance on the Lady Beetle Harmonia axyridis Mediated by the Soybean Aphid Aphis glycines
(North Dakota State University, 2010) Thurn, Anne Christine
Plants can directly and indirectly influence the natural enemies of their herbivores. Such trophic level effects apply to plants in natural and agronomic settings as well as to plants bred for pest resistance and biological control of herbivores. The effects of host plant resistance on herbivore natural enemies are highly variable, depending on the system. Currently, there is great interest in breeding soybean for resistance to the soybean aphid (Aphis glycines Matsumura). However, little is known about the effects of soybean aphid resistance traits on soybean aphid natural enemies. This study looks at the indirect effects of plant resistance to soybean aphid on the lady beetle Harmonia axyridis Pallas (Coleoptera: Coccinellidae ), an important natural enemy of the soybean aphid, using seven soybean varieties that exhibited variable resistance 1o the soybean aphid. Aphids were collected from greenhouse-reared soybean plants and fed to beetles in the laboratory. Harmonia. axyridis larval development time, adult mass, and fecundity over a month were measured. Results indicated moderate and inconsistent indirect effects with highly resistant plant varieties while some moderately-resistant plant varieties reduced adult weight and egg production. My conclusion is that soybean aphid resistance is potentially compatible with H. axyridis biological control, but care must be taken when selecting varieties if there is more than one source of resistance or if plant resistance differentially affects soybean aphids and their natural enemies.
Effects of Temperature on Pea Aphids, their Host Plants, and their Parasitoids
(North Dakota State University, 2018) Valls, Aleix
Temperature has the potential to alter every aspect of an organism’s biology. This is especially true when we focus on small ectotherms such as insects. Understanding the effects of temperature on insects is particularly important given that climate change scenarios predict changes in temperature across the globe. In Chapter 1 we explored the effects of heat shocks on a discrete host-parasitoid interaction, specifically asking what happens if the heat shock happened before, during or after the interaction. We found that heat shocks had a stronger negative effect when they occurred while the wasp was actively foraging. In a follow-up behavioral experiment, we observed that this result is likely caused by the heat shock quickly rendering the majority of wasps inactive. In Chapter 2 we tested how variation in temperature affects pea aphid population size and how the effect changes with average temperature. We compared the population size of pea aphids under constant and fluctuating temperature profiles across a cool temperature range (20C and 16C/24C) and a warm temperature range (28C and 24C/32C). We saw that in the cooler range, pea aphids in the constant and fluctuating temperature treatments had the same population size. However, the same was not true for the warmer temperatures. In that case, fluctuating temperature profiles produced smaller populations compared to the constant temperatures. In Chapter 3 we focused on the possible indirect effects of temperature on pea aphids mediated by the aphids’ host plants. We performed five experiments where we manipulated the exposure temperature (16C, 24C, and 32C) for plants and aphids. While temperature had strong direct effects on aphids and also affected plant size, temperature had little to no indirect effects on pea aphid fecundity. While the idea of temperature change can seem straightforward, temperature effects on insects are not straightforward. Timing and variation of temperature change are important. Indirect effects though direct effects on hosts also are important. My work shows a number of approaches for investigating these different temperature effects to better understand what might happen to insects when climate changes.
Exploring Effects of Weed Management in Agroecosystems: Arthropods, Soil Properties and Soybean Production
(North Dakota State University, 2014) Hansen, Ashton Anne
Soil-dwelling arthropods contribute to agroecosystems, but it’s unclear how specific taxa respond to weed management practices. Objectives were to explore 1) response of Collembola to weed management in a glyphosate-tolerant soybean system and 2) impacts of weed management and soil arthropod reduction (via insecticide) on soil and plant parameters. Weed management had variable effects on Collembola, whereas location had a consistent effect on diversity and density. Increased weed pressure decreased soil nitrate and reduced soybean yield. Reduction of soil arthropods didn’t impact soil nitrate or yield, but increased the number of soybean root nodules. This could be due to decreased root herbivores, or overcompensation of the plant. Previous research emphasized effects of plant communities on soil arthropods, but our study suggests soil properties strongly influence arthropod communities. Although this study does not show obvious benefits of soil arthropods, long term insecticide application may be detrimental to crop production.
A Faunal Survey of Coleoptera, Hemiptera (Heteroptera), and Lepidoptera Associated with Fraxinus Pennsylvanica Marshall (Oleaceae) in the Red River Valley of Eastern North Dakota
(North Dakota State University, 2014) Walker, James Samuel
The emerald ash borer (Agrilus planipennis; EAB) is an invasive wood-boring beetle causing mortality of ash trees in North America. This project was initiated because of the threat of EAB moving into North Dakota. The main objective was to establish a baseline of insects associated with ash (Fraxinus) in the Red River Valley of North Dakota before EAB arrives. Taxonomic groups focused on include: Coleoptera, Hemiptera (Heteroptera), and Lepidoptera. Ten sites were surveyed regularly. Sites were chosen due to their ash content: nine sites contained green ash (Fraxinus pennsylvanica), and one site contained black ash (F. nigra). Surveying was performed during the months of May through September in 2010 and 2011. Overall, 4,301 specimens from 53 families in three orders were identified in this study, totalling at least 276 distinct taxa. 23 of the species collected and identified in this study were found to be associated with Fraxinus.
Geographic Distribution and Effects of Transgenic Corn Hybrids and Chemical Insecticides on Northern and Western Corn Rootworms (Coleoptera: Chrysomelidae) in North Dakota
(North Dakota State University, 2018) Calles Torrez, Veronica
Northern (Diabrotica barberi Smith & Lawrence) and western (D. virgifera virgifera LeConte) corn rootworms are major corn (Zea mays L.) pests in North America. Integrated pest management (IPM) strategies used for corn rootworm control include crop rotation, chemical insecticides, and corn hybrids expressing Bacillus thuringiensis (Bt) toxins. Field and laboratory experiments were conducted between July 2013 and October 2017 to address the following objectives: 1) determine the geographic distribution and densities of D. barberi and D. v. virgifera in North Dakota (ND) and compare the effectiveness of unbaited green ScentryTM Multigard and yellow Pherocon® AM/NB sticky traps for monitoring both species; 2) access the impacts of corn hybrids expressing the Cry3Bb1, Cry34/35Ab1, and Cry3Bb1 + Cry34/35Ab1 proteins, tefluthrin soil insecticide, and clothianidin insecticidal seed treatment on beetle emergence, larval feeding injury, and corn grain yield; and 3) evaluate if either species has developed resistance to these Bt-proteins. Both species were commonly distributed in east-central and southeastern ND, and capture rates ranged from 0 to >10 beetles per trap per week. Green ScentryTM sticky traps captured greater mean numbers of D. barberi beetles in 68% of fields containing this species, while the yellow Pherocon AM/NB trap captured higher mean numbers of D. v. virgifera in 57% of fields containing this species, but their relative trap efficiency was inconclusive. Overall beetle emergence was significantly lower in Bt-protected than in non-Bt corn. Bt hybrids produced higher grain yield and sustained consistently lower levels of larval root-feeding injury than non-Bt in fields with higher rootworm densities. Tefluthrin and clothianidin did not significantly impact beetle emergence or larval root injury. Results also documented the first confirmed field-evolved incomplete resistance in D. barberi populations to Cry3Bb1 and Cry34/35Ab1 proteins. The Ransom population of D. v. virgifera was confirmed as resistant to the Cry3Bb1 toxin. Theses findings indicate reduced efficacy of corn rootworm control using tefluthrin, clothianidin, and Bt corn. Continuously scouting for rootworms using sticky traps or other methods prior to making rootworm management decisions, and the use of an IPM approach to their control is needed to mitigate the development of Bt-resistance rootworms in ND.
IfSAR DTM-derived Predictive Flood Models: A Cost-effective Approach to Target Site- Specific Mosquito (Diptera: Culicidae) Control Efforts
(North Dakota State University, 2016) Stenehjem, Jacquelin J.
The study area is the 400 km2 floodplain and wetlands of the upper Missouri River, located in the northwestern corner of North Dakota, near the community of Williston. Regional climate is semiarid, yet the Williston vector control agency battles large populations of Culicidae nearly every spring and summer. Best mosquito management practices (BMPs) are integrated, relying on a combination of thorough, routine, ground-based sampling and surveillance methods to provide important information on which control strategies and evaluations of effective are based. However, the mosquito breeding habitat near Williston is extensive and contains difficult terrain, which makes standard ground-based sampling and surveillance methods impractical. This study analyzed remotely sensed Interferometric Synthetic Aperture Radar (IfSAR) Digital Terrain Model (DTM) elevation data as a potential alternative for ground-based methods. Remotely sensed IfSAR technology is relative low-cost, has high-spatial resolution, is not limited by inclement weather, and only needs to be collected once if local topography remains stable. IfSAR elevation data provides information needed to model hydrological characteristics such as slope, aspect, water flow direction, and accumulation, important considerations in relation to mosquito control efforts. Predictive flood models, developed in this study from the IfSAR elevation data, make it possible to predict the locations of water accumulation within the floodplain as river elevations fluctuate. A vertical root mean squares error (RMSEz) assessment of the full IfSAR elevation data in all land cover classifications combined was 1.071 m, consistent with the vendor’s stated RMSEz of 1 meter. The vertical accuracy of the full IfSAR data was 2.099 meters at the 95% confidence level and is consistent with the 95th percentile accuracy of 2.211 meters. The frequency distribution of errors was generally normal. This study determined that airborne, high-resolution IfSAR DTM-elevation data can serve as an alternative for ground-based sampling and surveillance methods and provide a needed decision support system (DSS) tool to the local vector control agency. The predictive flood models are a new approach for predicting the locations of accumulated water within the floodplain will decrease vector control response time and improve the targeting of site-specific control efforts, which in turn, will decrease overall costs for these services.
Impact of Ragl Aphid Resistant Soybeans on Binodoxys communis (Gahan) (Hymenoptera: Braconidae), a Parasitoid of Soybean Aphid Aphis glycines Matsumura (Hemiptera: Aphididae )
(North Dakota State University, 2011) Ghising, Kiran
After its discovery in North America during the summer of 2000, the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae) became a major pest of the soybean, Glycine max (L.) Merr., in most soybean growing regions of the United States. The use of insect-resistant plant varieties and natural enemies, important components of Integrated Pest Management (IPM), when applied solely have the potential to be effective measures for controlling soybean aphids. However, resistant host plants may influence natural enemies in beneficial or detrimental ways, thereby altering their effectiveness when the two strategies are combined. Therefore, we investigated how a resistant variety impacts fitness of a biological control agent to understand its compatibility for pest management of the soybean aphid. A near isogenic susceptible soybean variety without the Ragl gene and a resistant variety with the Ragl gene were used to determine the effect of the Ragl on the development and fitness of the soybean aphid parasitoid, Binodoxys communis Gahan (Hymenoptera: Braconidae). Before testing for effects of the Ragl gene on the parasitoid, we first validated the expression of the Ragl gene and confirmed that these plants were resistant to soybean aphids by determining the growth rate of soybean aphids on both resistant and susceptible plants. The soybean aphid population and per capita growth rate were significantly higher when reared on susceptible soybean plants compared to resistant plants. In addition, polymerase chain reaction (PCR) was used to verify the genotypes and the presence of the Ragl gene in some of the plants used in the growth rate experiment. Results of the soybean aphid growth rate experiment combined with the results of the PCR helped to validate the expression of the Raglin the resistant plants used in our experiments. To determine the impact of these resistant plants on parasitoids, the total numbers of mummies (parasitized soybean aphids) produced and adult parasitoid emergence were compared for parasitoids that were given aphid hosts from either susceptible or resistant plants. Parasitoid fitness was measured in terms of parasitoid development time, their body length, and their metatibiae length. We found a higher number of mummies in susceptible soybean plants than in the resistant plants as well as a higher emergence rate of adult parasitoids from the mummies reared on susceptible plants. The development time from mummy to adult parasitoid emergence was only one day longer with aphid hosts from resistant plants compared to susceptible plants. Despite some difference in the size of parasitoids from resistant and susceptible plants, very few parasitoids completed development on resistant plants. In summary, our results indicate poorer establishment and reproductive performance of B. communis from soybean aphids on resistant plants compared to soybean aphids on susceptible plants. This suggests that widespread adoption of resistant soybean plants might be detrimental to the overall sustainability of this parasitoid and its ability to help control soybean aphids. We did, however, find that at least some B. communis could successfully develop and emerge on soybean aphids from resistant plants, suggesting that there is at least some possibility that the parasitoid could survive and assist in aphid management even if the Rag 1 resistant plants become commonplace. The parasitoid's relative fitness and reproductive output will likely play important roles in ultimately determining the short- and long-term compatibility of utilizing both B. communis and resistant soybean plants for soybean aphid control.
Impacts of Microbial Seed Inoculants on Growth of Field Pea (Pisum sativum L.), and Implications for Plant-insect Interactions
(North Dakota State University, 2021) Glogoza, Benjamin Patrick
Soil microbes that associate with plant roots can benefit plants by increasing the supply or availability of nutrients to increase the plant’s resilience to abiotic and biotic stress, crop germination rates, root and shoot growth, flower production, and yield. We evaluated the impact of five commercially available treatments: 1) B5, Bacillus bacteria, 2) GP, Trichoderma fungi, 3) N2, Paenibacillus nitrogen-fixing bacteria, 4) combination of B5+GP+N2, and 5) water control, and soil-dwelling Collembola on growth and biomass distribution of the specialty crop field pea in a greenhouse setting. We assessed plant growth (e.g., height, biomass of shoots and roots) and results showed that microbial inoculants positively impacted field pea plant growth under specific abiotic environmental stresses.
Influence of Neonicotinoid Seed Treatment on Two Co-Occuring Arthropod Pests, Two-Spotted Spider Mite (Tetranychus urticae) and Western Flower Thrips (Frankliniella occidentalis)
(North Dakota State University, 2019) Brenner, Robert J
Insecticidal neonicotinoid seed treatments in agriculture is a common insect pest management strategy. Seed treatments have systemic and residual toxicity, which are effective against target insect pests. However, effects on other arthropod pests is less straightforward. We evaluated the effects of a neonicotinoid seed treatment, thiamethoxam, on two soybean pests, herbivorous two-spotted spider mites (Tetranychus urticae Koch) and an omnivore and facultative predator of spider mite eggs, western flower thrips (Frankliniella occidentalis Pergande). We used greenhouse and laboratory experiments to evaluate thiamethoxam soybean seed treatments on spider mite densities and thrips omnivorous feeding behavior. Our results suggest seed treatment may encourage spider mite reproduction and influence thrips herbivory over egg predation when both resources are available. Implications of this study highlight the use of thiamethoxam soybean seed treatment as a potential contributor to increased spider mite populations, thrips reduced role as spider mite predator, and increased role as herbivorous pest.
Integrated Pest Management of Soybean Aphid (Aphis glycines) in North Dakota
(North Dakota State University, 2010) Hochhalter, Julie
The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a major pest of soybean (Glycine max L.). This aphid is a native of Asia and was first discovered in the United States in Wisconsin in July 2000, and in North Dakota in summer 2001. Management of the soybean aphid varies across the geographical range of the pest. The impact of the soybean aphid has been less in North Dakota compared to many areas of the Midwest. One reason is environmental conditions in North Dakota limits population growth of the soybean aphid. Another is that until recently the area of soybean hectares in North Dakota has been limited. But now production has increased and growers are expecting integrated pest management programs designed specifically for North Dakota conditions. This research addresses how insecticides and resistant soybean cultivars might be used to control North Dakota populations of the soybean aphid. The objective of the first study was to determine efficacy of foliar and seed treatments for controlling the soybean aphid. Effects on beneficial insects were also determined. The foliar insecticide lambda-cyhalothrin (Warrior) was applied to soybean at different plant growth stages. The seed treatment thiamethoxam (Cruiser Maxx) was applied alone and in combination with the foliar insecticide lambda-cyhalothrin (Warrior). A foliar application of lambda-cyhalothrin (Warrior) applied at the economic threshold of 250 aphids per plant was the most effective control method. Seed treatments were not effective, probably because insecticidal effects had declined by the time aphids were invading the crop. The objective of the second study was to evaluate experimental soybean lines for resistance to soybean aphid. The first experiment was conducted in the greenhouse and involved 436 soybean lines. The second experiment included 30 susceptible lines and 25 resistant soybean lines at two field sites. The third experiment included the same lines that were evaluated in the field, but this screening was conducted in the greenhouse and involved caging aphids. In general, ranking of the lines for resistance was consistent between the first greenhouse experiment and the field experiment, suggesting that greenhouse screening is an effective method for scoring soybean lines for resistance and can be used to accelerate progress in soybean breeding programs. Five experimental lines, known to have the Ragl gene that confers resistance to soybean aphid, maintained aphid levels below the economic injury level. The economic injury level is 674 aphids per plant when the plant is at the reproductive stages. The third experiment, which caged aphids on leaves of susceptible and resistant lines in the greenhouse, was not an effective method for scoring resistance.
Investigating the Subspecific Designation of Euschistus servus (Say) (Hemiptera: Heteroptera: Pentatomidae) Using a Combined Landmark-Based Geometric Morphometrics Approach
(North Dakota State University, 2021) Oliveras, Vincent Aron
Euschistus servus is currently subdivided into two subspecies: E. s. servus and E. s. euschistoides. An intergrade population inhabits the central U.S. This study sought to reevaluate the established subspecific designations and determine whether E. servus subspecies and intergrade populations express distinct taxonomically important morphological characteristics throughout the U.S. We quantified landmark-based geometric morphometric data in conjunction with traditional morphometrics from specimens collected along a wide geographic area and used a principal component analysis to determine if there is a significant difference within the subspecies’ morphology, assessing shape between morphogroups failed to produce clusters commensurate to the E. s. servus and E. s. euschistoides forms. Further analysis suggested that there is linear relationship between the taxonomic characters and latitude which may be indicative of clinal variation. This data indicates E. servus should be recognized as polymorphic as opposed to polytypic, disputing the subspecific designation of the E. servus subspecies complex.

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