Entomology Masters Theses

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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.
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.
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.
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.
Oviposition Preference and Larval Host Range of the Sugarbeet Root Maggot
(North Dakota State University, 2012) Msangosoko, Kondwani Richmond
The sugarbeet root maggot, Tetanops myopaeformis Röder, is native to North America; however, its main crop host, sugarbeet, Beta vulgaris L., was introduced to the continent from Europe. This study involved an investigation of the attractiveness of cultivated crops and native North American weed species for oviposition by T. myopaeformis and the relative suitability of these potential host plant species for larval development, thus potentially shedding light on the native and current host range of this pest. Females preferred to oviposit near the following plant species: sugarbeet; spinach, Spinacia oleroceae L.; palmer amaranth, Amaranthus palmeri S. Watts.; common lambsquarters, Chenopodium album L.; redroot pigweed, Amaranthus retroflexus L.; and spear saltbush, Atriplex patula L. Larval survival was highest on spinach, followed by sugarbeet, and spear saltbush (all belonging to the family Chenopodiaceae). This suggests that species within this family likely served as native host plants for T. myopaeformis before the introduction of sugarbeet to North America. Lower larval numbers on common lambsquarters, redroot pigweed, and Palmer amaranth suggest that these species are sub-optimal hosts, despite being attractive for oviposition. Additional findings showed a general lack of oviposition preference by T. myopaeformis females for sunflower, Helianthus annuus L., and common ragweed, Ambrosia artemisiifolia L. These results provide further insights into the rapidly successful host preference shift by this insect to sugarbeet.
Pest Management of Wheat Stem Sawfly, Cephus Cinctus Norton (Hymenoptera: Cephidae), in Western North Dakota
(North Dakota State University, 2012) Stegmiller, Joseph
The wheat stem sawfly, Cephus cinctus Norton, is regarded as a major pest of dryland wheat in the Upper Great Plains. For peak emergence of wheat stem sawfly, the most accurate base was 0 C using air temperature, and then degree-day base of 0 C using soil temperatures. For Bracon cephi, the most accurate base temperature was the lower degree-day base using air (0 C) and soil (0 C) temperatures. The solid-stemmed varieties, Mott and Choteau, exhibited the highest stem solidity and also experienced the lowest percentage of wheat stem sawfly damaged stems. The hollow-stemmed varieties, Glenn, Reeder and Steele ND, had the lowest levels of solidity and usually the highest percentage of wheat stem sawfly damaged stems. When wheat stem sawfly populations were high, the solid-stemmed wheat varieties, Mott and Choteau, had yield, test weight, and protein that were comparable to the hollow-stemmed varieties, Glenn, Reeder and Steele ND.
The Tingidae (Hemiptera: Heteroptera) of Southern Central America (with an Emphasis on Costa Rica)
(North Dakota State University, 2018) Knudson, Alexander
The genera of Tingidae of the neotropics are herein diagnosed and a key for their identification is also provided. Five new genera are described from Central America, two from Panama, two from Costa Rica, and one new genus is described from Mexico. This brings the total of neotropical genera to 74. One new species, Mexibyrsa woolleyi is described from Mexico. The Tingidae of southern Central America (Nicaragua, Costa Rica, and Panama) are reviewed in detail. There are now 153 described species spread among 43 genera. Thirty-two new species from southern Central America are described. Identification keys are provided for all species found in the study region.

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