MITPPC Research publications
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Item Minnesota's Top 124 Terrestrial Invasive Plants and Pests: Priorities for Research(2016) Minnesota Invasive Terrestrial Plants and Pests CenterThis document, “Minnesota’s Top 124 Terrestrial Invasive Plants and Pests: Priorities for Research,” describes the outcome of efforts to identify which invasive species pose the greatest threats to Minnesota’s forests, prairies, wetlands, and agriculture. This information will be used to set funding priorities for the Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC) at the University of Minnesota. Funding needs for research on terrestrial invasive species far exceed the resources that are currently available. Thus, a fair, consistent, and transparent process to determine priorities for future research is essential. Those priorities will be reflected in regular requests for proposals. The lists in this report do not supersede agency regulatory lists or management priorities. For example, the Noxious Weed Advisory Committee has a risk assessment process to identify harmful plants that threaten the state and recommend appropriate regulatory and management actions. Existing risk assessments were consulted as the species in this prioritization were evaluated.Item Microbial separation from a complex matrix by a hand-held microfluidic device(Chemical Communications (Cambridge, England), 2017) Singh, Renu; Brockgreitens, John; Saiapina, Olga; Wu, Yan; Abbas, AbdennourThrough a simple chemical activation of biomolecules present in the outer structures of microbial cells, microorganisms can be rapidly isolated on gold-coated surfaces in a microfluidic device with over 99% capture efficiency. Bacterial and fungal cells can be selectively captured, concentrated and retrieved for further analysis.Item Potential Causes of Declines in Minnesota’s Prairie Butterflies with a Focus on Insecticidal Control of the Soybean Aphid(Minnesota Invasive Terrestrial Plants and Pests Center, University of Minnesota, 2017-03-20) Runquist, Erik; Heimpel, George E.Minnesota is home to diverse prairie butterfly fauna, but several species have recently undergone drastic population declines. For example, 10 of the 15 butterfly species classified as Endangered, Threatened, and of Special Concern by the State of Minnesota depend exclusively on native prairies. The declines of two of these, the Dakota Skipper and the Poweshiek Skipperling, have been so precipitous that they are now exceedingly rare despite having been predictably common previously. Poweshiek Skipperling is now on the verge of global extinction. Multiple regional and local factors may have contributed to these declines, and those factors are expected to have interacted in various ways. However, a working hypothesis is that these butterfly declines are at least in part the result of insecticide drift related to management of the soybean aphid, which invaded Minnesota in 2000 and led to substantial increases in insecticide applications to soybeans. On November 15, 2016, the Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC) in collaboration with the University of Minnesota Institute on the Environment held a workshop to assess hypotheses that could explain the butterfly declines. The workshop featured seven speakers from the US Fish and Wildlife Service, Minnesota Department of Natural Resources, Minnesota Zoo, University of Minnesota, and Environmental Protection Agency. The presentations, which MITPPC has posted online (http://z.umn.edu/mitppcbutterfly), focused on three themes: (i) biology and conservation status of the endangered butterflies, (ii) the possible role of soybean aphid management in affecting butterfly populations, and (iii) risk assessment and potential solutions via conservation measures. The workshop fostered collaboration between experts in prairie conservation and agricultural pest management and featured extensive discussion between participants following the presentations. Members of the conservation and agricultural communities are typically not afforded the chance to engage in conversations of this type and discussions were particularly fruitful for information sharing and relationship building. This document synthesizes the findings of the workshop and provides guidance to the MITPPC on a needed integrative research program studying the non-target consequences of invasive soybean aphid management on Minnesota’s endangered prairie butterflies. We conclude that skipper conservation will be advanced through a new research program that includes tests of the hypothesis that soybean aphid insecticides are contributing to skipper declines. Targeted research is needed to assess 1) the extent of insecticide exposure the butterflies may experience in the wild and 2) the biological consequences of those exposures using replicated controlled experiments. Ongoing drift studies conducted by the Minnesota Zoo and US Fish and Wildlife Service (see below) have provided important preliminary links to soybean aphid insecticides, but significantly more data is needed to really understand wild exposure dynamics. Controlled exposure experiments may soon be launched by Minnesota Zoo and University of Minnesota researchers, but those experiments are currently funding- and personnel-limited and cannot address the full range of needed tests. The MITPPC can play a leading role by supporting and expanding critical comprehensive research on potential non-target effects of management against an invasive pest.Item Efficacy of organic and conventional insecticides for Drosophila suzukii when combined with erythritol, a non-nutritive feeding stimulant(Crop Protection, 2019) Gullickson, Matthew G.; Rogers, Mary A.; Burkness, Eric C.; Hutchison, W.D.Spotted-wing drosophila (Drosophila suzukii; SWD) is an economically important insect pest of small and soft skinned fruit. Female SWD use a heavily sclerotized ovipositor to deposit eggs in ripening fruit. After emergence from eggs, larval feeding and development damages fruit and results in yield loss. The most prevalent management strategy continues to be regular applications of broad-spectrum insecticides. Since the arrival of SWD and the subsequent increase of insecticidal sprays, producers are challenged to balance goals related to pest and pollinator management, the environment, and finances. Growers need additional management tools in order to reduce environmental risks and to adhere to label specifications. To this end, we investigated the efficacy of novel chemical controls alone and with the addition of feeding stimulants and surfactants, compared to standard insecticide products typically used for pest management by fruit growers. We conducted a series of laboratory bioassays to test four organically approved insecticides, three conventional insecticides, one feeding stimulant and five adjuvants. We measured the effects of these products on SWD adult mortality, oviposition, larval and pupal development, and adult emergence. Nine of the 25 treatments significantly increased adult mortality after 24 h of exposure and only three of the 25 treatments significantly reduced oviposition. The addition of erythritol [1.75 M] to some marginally effective insecticides increased their efficacy, while decreasing the efficacy of others. This information will guide future research and result in recommendations for both organic and conventional growers for sustainable management of this invasive pest. •Laboratory study of 25 treatments on Drosophila suzukii mortality and development.•Erythritol, GS-omega/kappa-Hxtx-Hv1a, and novaluron increased D. suzukii mortality.•Erythritol inconsistently increased efficacy of insecticides on D. suzukii.•Non-nutritive feeding stimulant treatments did not decrease D. suzukii oviposition.Item Observability and Performance Analysis of a Model-Free Synthetic Air Data Estimator(Journal of Aircraft, 2019) Sun, Kerry; Regan, Christopher D; Gebre-Egziabher, DemozThe performance, accuracy, and observability of a model-free angle of attack and angle of sideslip estimator are presented. The estimator does not require an aircraft dynamic model; rather, it only relies on measurements from a GPS receiver, an inertial measurement unit, and a pitot tube. The estimator is an inertial navigation system (INS)/GPS extended Kalman filter augmented with the states to account for wind and an additional measurement from a pitot tube. It is shown that the estimator is conditionally observable. Conditions (maneuvers) that enhance its observability are identified. A bound on the angle of attack and angle of sideslip estimate uncertainties is derived. The effect of INS/GPS, horizontal and vertical wind uncertainty on the accuracy of angle of attack and angle of sideslip estimate is assessed. Simulation and flight-test results of the method are presented. The results show that the 1−σ bound on a small, slow-flying unmanned aerial vehicle for angle of attack and sideslip angle estimates are about 5 and 3 deg, respectively.Item Foliage Type and Deprivation Alters the Movement Behavior of Late Instar European Gypsy Moth Lymantria dispar (Lepidoptera: Erebidae)(Journal of Insect Behavior, 2019-04) Wittman, Jacob T.; Aukema, Brian H.The movement behavior of insects characterizes their ability to disperse, establish, compete, forage, seek mates, and ultimately reproduce. Understanding the movement of invasive insects is particularly important for developing management policies. We conducted laboratory experiments in Minnesota, USA to determine how host type and food deprivation affected the movement of late instars of the European gypsy moth Lymantria dispar (Lepidoptera: Erebidae), an invasive forest insect in North America. Gypsy moth larvae can feed on over 300 species of trees and shrubs. During outbreaks food availability to conspecifics can become severely restricted as developing instars consume increasing amounts of foliage. Larvae were raised on one of five foods: Quercus macrocarpa , Larix laricina , Acer platanoides , Acer saccharinum , or artificial diet. Subsets of fifth and sixth instar larvae were also deprived of food for zero, 24, or 48 h. After the food deprivation period, late instar larvae were placed on a servosphere and their movement paths were recorded. Larvae raised on Q. macrocarpa , a preferred host, were unlikely to move unless starved. They moved farther the longer they were starved. In contrast, when larvae were raised on less preferred hosts, they were more likely to move without prior starvation. These results suggest that feeding on optimal hosts provides gypsy moth larvae with the energy and nutritional requirements to move more quickly to more food when there is none immediately available.Item Species Distribution Model Projections for Incipient Invasive Species of Minnesota(2019-05-20) Briscoe Runquist, Ryan D.; Lake, Thomas; Moeller, David A.Invasive species are marked by rapid range expansions or dramatic population growth that negatively affects ecosystems and communities outside of their historical range (Valéry et al. 2008). Because invasive species often cause considerable economic losses, land managers and conservation scientists need tools to forecast invasion risk so that they can direct resources for prevention strategies and targeted surveillance operations (Peterson and Robins 2003; Underwood et al. 2004; Thuiller et al. 2005; Loo et al. 2007; Bradley et al. 2010). Species distribution models (SDM) use species occurrence records and environmental data to build correlative models of habitat suitability and identify key environmental variables limiting range expansion (Elith and Leathwick 2009a, b; Elith et al. 2010; Elith et al. 2011). For invasive species, SDMs can be a useful tool for identifying potential habitat requirements and environmental limitations of future range expansion (Bradley et al. 2009; Bradley et al. 2010; Elith et al. 2010; Allen and Bradley 2016). In this document, we provide detailed distribution models for eight invasive species incipient to the Upper Midwest. These species are invasive to portions of North America and were identified by the Minnesota Invasive Terrestrial Plants and Pests (MITPPC) Center as not present or incipient invasions to Minnesota with potential to have economic and natural resources impacts if they were to successfully invade Minnesota. We assess of habitat suitability for these species across the state under current climate conditions and under a range of future climate scenarios. The incipient invasive species included in this document are: Palmer Amaranth (Amaranthus palmeri); Black Swallowwort (Vincetoxicum nigrum); Common Teasel (Dipsacus fullonum); Brown Knapweed (Centaurea jacea); Dalmatian Toadflax (Linaria dalmatica); Oriental Bittersweet (Celastrus orbiculatus); Japanese Hops (Humulus japonicus); Narrowleaf Bittercress (Cardamine impatiens). Additionally, this document contains distributional information on two invasive species that have invaded Minnesota and spread rapidly, causing measurable ecological and economic damage. Both species have established populations in portions of the state that are subject to control and eradication efforts. The models contained in this document provide further information on the potential for spread and establishment throughout the state. The established and top priority species are: Wild Parsnip (Pastinaca sativa); Common Tansy (Tanacetum vulgare).Item Detection of Stress Induced by Soybean Aphid (Hemiptera: Aphididae) Using Multispectral Imagery from Unmanned Aerial Vehicles(Journal of Economic Entomology, 2019-11) Marston, Zachary P. D.; Cira, Theresa M.; Hodgson, Erin W.; Knight, Joseph F.; MacRae, Ian V.; Koch, Robert L.Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a common pest of soybean, Glycine max (L.) Merrill (Fabales: Fabaceae), in North America requiring frequent scouting as part of an integrated pest management plan. Current scouting methods are time consuming and provide incomplete coverage of soybean. Unmanned aerial vehicles (UAVs) are capable of collecting high-resolution imagery that offer more detailed coverage in agricultural fields than traditional scouting methods. Recently, it was documented that changes to the spectral reflectance of soybean canopies caused by aphid-induced stress could be detected from ground-based sensors; however, it remained unknown whether these changes could also be detected from UAV-based sensors. Small-plot trials were conducted in 2017 and 2018 where cages were used to manipulate aphid populations. Additional open-field trials were conducted in 2018 where insecticides were used to create a gradient of aphid pressure. Whole-plant soybean aphid densities were recorded along with UAV-based multispectral imagery. Simple linear regressions were used to determine whether UAV-based multispectral reflectance was associated with aphid populations. Our findings indicate that near-infrared reflectance decreased with increasing soybean aphid populations in caged trials when cumulative aphid days surpassed the economic injury level, and in open-field trials when soybean aphid populations were above the economic threshold. These findings provide the first documentation of soybean aphid-induced stress being detected from UAV-based multispectral imagery and advance the use of UAVs for remote scouting of soybean aphid and other field crop pests.Item Phenology matters: Extended spring and autumn canopy cover increases biotic resistance of forests to invasion by common buckthorn (Rhamnus cathartica)(Forest Ecology and Management, 2020) Schuster, Michael J.; Wragg, Peter D.; Williams, Laura J.; Butler, Ethan E.; Stefanski, Artur; Reich, Peter B.Forest light availability strongly regulates understory community composition, and low availability may confer resistance to invasion by exotic species, yet common buckthorn (Rhamnus cathartica L.) invades North American temperate forests with a broad range of light habitats. It is unclear to what extent buckthorn’s success is due to high mid-season shade tolerance versus shade avoidance permitted by early leaf out and late senescence. We used buckthorn seedlings planted into a forest diversity experiment in Cloquet, Minnesota, USA and a combined buckthorn physiology-canopy light model to test (1) how buckthorn germination, growth, and survival depend on canopy shading and (2) how canopy species richness and phenology affect light availability and buckthorn performance. Based on the mean of May, August, and October light measurements, we found that canopies that permitted ≤3% transmission of incoming light had almost complete mortality of buckthorn and that growth of surviving buckthorn was strongly tied to light availability, but not canopy richness. Compared to deciduous canopies or deciduous-evergreen mixtures, evergreen canopies restricted light availability the most and led to the smallest and least likely to survive buckthorn. Our canopy models further indicated a tight linkage between buckthorn performance and spring and autumn light availability, but not summer light availability. We conclude that spring and autumn light availability are key regulators of buckthorn performance and that buckthorn relies on shade avoidance via an extended phenology to succeed in temperate forests. Consequently, we suggest species with extended spring or autumn canopy cover offer the greatest resistance to invasion, and communities which are often leafless during such periods are most vulnerable to invasion by buckthorn and similar invasive shrubs.Item Density-dependent lifespan and estimation of life expectancy for a parasitoid with implications for population dynamics(Oecologia, 2020) Miksanek, James Rudolph; Heimpel, George E.Parasitoid lifespan is influenced by nutrient availability, thus the lifespan of parasitoids that rely on their hosts for nutritional resources (either via host feeding or by consuming honeydew) should vary with host density. We assessed the survival and reproduction of one such species, Aphelinus certus— a parasitoid of the soybean aphid, Aphis glycines —over a range of host densities using a laboratory assay. We found a positive, asymptotic relationship between host density and the lifespan and fecundity of A. certus that was supported by a traditional survivorship analysis as well as a logistic model. Parasitoids from this assay were also used to develop a wing wear index relating setae damage to parasitoid age. This index was used to estimate the life expectancy of field-collected parasitoids, which was shorter than the life expectancy of laboratory-reared female parasitoids. Finally, host-density-dependent parasitoid lifespan was incorporated into a coupled-equations matrix population model that revealed that decreasing the degree of host density dependence leads to higher equilibrium host densities and changes in the quality of equilibrium (e.g. stable limit cycles). These results detail the relatively unstudied phenomenon of host-density-dependent parasitoid lifespan and suggest that differences between laboratory- and field-determined parasitoid life expectancy have important implications for population dynamics and the biological control of insects.Item Goat Digestion Leads to Low Survival and Viability of Common Buckthorn (Rhamnus cathartica) Seeds(Natural Areas Journal, 2020) Marchetto, Katherine M.; Heuschele, D. Jo; Larkin, Daniel J.; Wolf, Tiffany M.The use of goat browsing for invasive plant management is growing in the United States, but many questions remain about the efficacy of goat browsing for invasive plant control. One common concern of land managers and other stakeholders is whether goats can spread invasive plants through endozoochory (seed dispersal via ingestion and excretion in feces). We evaluated this possibility using common buckthorn (Rhamnus cathartica), an invasive shrub for which goats are often employed as a control method. Goats were fed buckthorn berries, and their feces were collected and examined at 24 hr, 48 hr, and 72 hr post-ingestion for intact seeds that survived gut passage. A low proportion of buckthorn seeds (2%) made it through the goat digestive system intact. Of these, only 11% remained viable, compared to 63% viability of control seeds. We conclude that consumption of buckthorn fruits by goats effectively destroys seeds, indicating low risk of dispersal via gut passage. To put these results in context, and provide more guidance for land managers, we additionally reviewed literature investigating seed recovery following ingestion by goats. Based on a synthetic analysis across 28 plant species, we found that seeds >4 mm long were unlikely to be recovered from feces intact, while smaller seeds posed higher dispersal risk.Item Two-Stage Batch Algorithm for Nonlinear Static Parameter Estimation(Journal of Guidance, Control, and Dynamics, 2020) Kerry, Sun; Gebre-Egziabher, DemozA two-stage batch estimation algorithm for solving a class of nonlinear, static parameter estimation problems that appear in aerospace engineering applications is proposed. It is shown how these problems can be recast into a form suitable for the proposed two-stage estimation process. In the first stage, linear least squares is used to obtain a subset of the unknown parameters (set 1) and a residual sampling procedure is used for selecting initial values for the rest of the parameters (set 2). In the second stage, depending on the uniqueness of the local minimum, either only the parameters in the second set need to be re-estimated, or all the parameters will have to be re-estimated simultaneously, by a nonlinear constrained optimization. The estimates from the first stage are used as initial conditions for the second-stage optimizer. It is shown that this approach alleviates the sensitivity to initial conditions and minimizes the likelihood of converging to an incorrect local minimum of the nonlinear cost function. An error bound analysis is presented to show that the first stage can be solved in such a way that the total cost function will be driven to the optimal cost, and the difference has an upper bound. Two tutorial examples are used to show how to implement this estimator and compare its performance to other similar nonlinear estimators. Finally, the estimator is used on a 5-hole Pitot tube calibration problem using flight test data collected from a small unmanned aerial vehicle that cannot be easily solved with single-stage methods.Item A field-based assessment of the parasitoid Aphelinus certus as a biological control agent of soybean aphid in North America(Biological Control, 2020) Miksanek, James Rudolph; Heimpel, George E.Damaging outbreaks of soybean aphid continue to occur in North America despite the valuable biological control services provided by resident natural enemies. The adventive parasitoid Aphelinus certus Yasnosh (Hymenoptera: Aphelinidae) has recently established in North America and has been hypothesized to be a key component of the resident natural enemy community, but there have been few studies evaluating the efficacy of this parasitoid in suppressing soybean aphid populations. We used an exclusion cage study to quantify the effect of A. certus on soybean aphid population growth at four sites spanning western and east-central Minnesota from 2017 to 2019. There were minimal differences in soybean aphid population growth between experimental treatments that excluded natural enemies and control treatments, suggesting that parasitism of soybean aphid by A. certus did not have a strong impact on soybean aphid population growth during this study. Because, for example, A. certus larvae can reduce host reproduction prior to mortality (resulting in underestimates of effects in short-term studies), our results reflect the challenges of using exclusion cages to assess the effects of individual natural enemy species, especially those with complex life cycles.Item Minnesota’s top terrestrial invasive plants and pests for research: an expanded prioritization(Minnesota Invasive Terrestrial Plants and Pests Center, University of Minnesota, 2020-01) Venette, R.C.The Minnesota Invasive Terrestrial Plants and Pests Center has prioritized 168 terrestrial invasive species that are significant threats to the forests, prairies, wetlands, and agriculture within Minnesota. The highest-priority threats are eligible for research funded by MITPPC. Among insects and earthworms, eligible species are (1) Dendroctonus ponderosae; (2) Agrilus planipennis and A. biguttatus; (3) Aphis glycines; (4) Amynthas spp.; (5) Lymantria dispar dispar and L. dispar asiatica (6) Halyomorpha halys; (7) Scolytus schevyrewi and S. multistriatus; (8) Popillia japonica; (9) Anoplophora glabripennis; (10) Eupoecilia ambiguella; (11) Helicoverpa armigera; (12) Sirex noctilio; (13) Drosophila suzukii; (14) Spodoptera littoralis; and (15) Tetropium fuscum. Japanese beetle, Popillia japonica, became eligible after new information was considered in the assessment. Among plant pathogens, eligible species are (1) Ophiostoma novo-ulmi; (2) Ceratocystis fagacearum; (3) Raffaelea quercivora; (4) Globodera pallida and Globodera rostochiensis; (5) Heterobasidion irregulare; (6) Heterodera latipons and H. filipjevi; (7) Phytophthora ramorum; (8) Geosmithia morbida; (9) Phyllachora maydis, (10) Aster yellows phytoplasma; (11) Ralstonia solanacearum, Race 3, biovar 2; (12) Cronartium ribicola; (13) Hymenoscyphus fraxineus; (14) Tilletia controversa (cereal strain); and (15) Fusarium virguliforme. Corn tar spot caused by Phyllachora maydis was detected in Minnesota for the first time in 2019 and assessed by MITPPC in the same year. Among plants, eligible species are (1) Typha angustifolia; (2) Lonicera maackii, L. morrowii, L. tatarica, and L. japonica; (3) Berberis x ottawensis; (4) Centaurea stoebe ssp. micranthos and C. diffusa; (5) Tanacetum vulgare; (6) Frangula alnus and Rhamnus cathartica; (7) Phragmites australis subsp. australis; (8) Gypsophila paniculata; (9) Lupinus polyphyllus; (10) Cirsium arvense; (11) Microstegium vimineum; (12) Cotoneaster lucidus; (13) Ailanthus altissima; (14) Amaranthus palmeri; and (15) Euphorbia esula. Narrowleaf cattail, Typha angustifolia, Amur honeysuckle, Lonicera maackii, Japanese honeysuckle, L. japonica, a barberry hybrid, Berberis x ottawensis, diffuse knapweed, Centaurea diffusa, baby’s breath, Gypsophila paniculata, Japanese stiltgrass, Microstegium vimineum, large- leaved lupine, Lupinus polyphyllus, hedge cotoneaster, Cotoneaster lucidus, and tree of heaven, Ailanthus altissima were newly nominated since the previous assessment. This ranking of terrestrial invasive species threats is the most extensive regionally and to our knowledge is second only to national rankings prepared by the Animal and Plant Health Inspection Service of the US Department of Agriculture.Item Increased light availability due to forestry mowing of invasive European buckthorn promotes its regeneration(Restoration Ecology, 2020-03) Anfang, Carl; Schuster, Michael J.; Wragg, Peter D.; Reich, Peter B.The invasive shrub Rhamnus cathartica L. (common buckthorn) dominates the understory of many temperate forests of eastern North America. Common buckthorn outcompetes native understory species for light, forming monospecific stands that suppress plant and animal diversity. Removing common buckthorn is a common management priority within its invasive range. In recent years, forestry mowing has become popular in removing common buckthorn. This control method removes a midstory of common buckthorn, increasing light availability to the lower understory (which could favor buckthorn regeneration) and creating a layer of mulch on the forest floor (which could suppress buckthorn regeneration). Here we investigate whether and how increased light availability and increased ground cover (mulch) resulting from forestry mowing affects buckthorn regeneration from the seed bank. We evaluated buckthorn germination, survival, and early growth in response to a factorial combination of shading treatments and buckthorn mulch depth treatments in an oak forest in Minnesota, U.S.A. Increased light availability increased buckthorn seedling survival and growth, whereas increased mulch depth did not significantly affect the number of buckthorn establishing from seed over one growing season and winter. Thus, removing buckthorn by forestry mowing (or any other method) is likely to facilitate buckthorn reestablishment by increasing light availability at the ground.Item Population Ecology Of Aphelinus Certus, An Adventive Parasitoid Of Soybean Aphid In North America, With Implications For Biological Control(2020-05) Miksanek, JamesParasitoids are excellent model systems in addressing fundamental aspects of biology and ecology while offering a high degree of economic and ecological value in regulating the population densities of their host species in both natural and agroecological settings. The single most important arthropod pest of soybean is the soybean aphid (Aphis glycines). Although not recommended for release due to its broad host range, the parasitoid Aphelinus certus has since been accidentally introduced into North America and has been hypothesized to be a key natural enemy of soybean aphid. However, the overall impact of A. certus in the biological control of soybean aphid is uncertain. The chapters in this thesis are united by broader theories and concepts addressing the role of A. certus in biological control. Chapter 1 presents a coupled-equations matrix population model parameterized by a series of laboratory bioassays outlining the life history of soybean aphid and A. certus; analysis of the model suggested that a parasitism rate of 0.21 d−1, which would be equivalent to at least 3.4% mummies, is capable of maintaining soybean aphid below economically damaging levels in 31.0% of simulations. Chapter 2 further explores the effects of host density on parasitoid lifespan and reproduction as well as establishes a quantitative wing wear index for estimating the age of field-collected parasitoids. Moving from theoretical to in-field efficacy, Chapter 3 evaluates the impact of A. certus on soybean aphid in soybean fields across central and western Minnesota (United States) from 2017–2019; contrary to the predictions of the model in Chapter 1, the results of this field experiment did not find a strong effect of A. certus in reducing the population growth rates of soybean aphid. Finally, Chapter 4 evaluates the prevalence of parasitism by A. certus on the native aphid species Aphis asclepiadis and Aphis monardae in prairie ecosystems; these results suggest that A. certus readily colonizes or is already established in natural habitats and poses a potential threat to endemic aphid populations. Lastly, I offer conclusions by more broadly discussing this work within the context of population dynamics, ecology, and biological control.Item Fosamine ammonium impacts on the targeted invasive shrub Rhamnus cathartica and non-target herbs(Invasive Plant Science and Management, 2020-06) Schuster, Michael J.; Bockenstedt, Paul; Wragg, Peter D.; Reich, Peter B.Fosamine ammonium (Krenite®) is a foliar herbicide that primarily targets woody plant species; however, formal evaluations of its efficacy and potential for non-target impacts are scarce in the literature. The few tests of fosamine ammonium that exist focus primarily on its use in open environments, and the value of fosamine ammonium in controlling invasive understory shrubs is unclear. Here, we test the impact of fosamine ammonium on invasive common buckthorn (Rhamnus cathartica L.) and co-occurring herbaceous plants across six forest sites in Minnesota, USA. Rhamnus cathartica treated with fosamine ammonium had a 95% mortality rate, indicating high efficacy of fosamine ammonium for use against R. cathartica. Non-target impacts varied between forbs and graminoids such that forb cover was reduced by up to 85%, depending on site, whereas graminoid cover was sparse and impacts of fosamine ammonium on graminoids were unclear. These results indicate that while fosamine ammonium can provide effective control of R. cathartica and other understory shrubs, there is potential for significant non-target impacts following its use. We therefore suggest that land managers carefully consider the timing, rate, and application method of fosamine ammonium to achieve desired target and non-target impacts.Item Improving Stink Bug Management in The Midwest: Understanding Dispersal Capacity and Developing Sampling Plans(2020-12) Carlesso Aita, RafaelStink bugs are an emerging threat for horticultural and field crops in the North Central Region of the United States. This threat can be attributed to the increase in abundance of Pentatomidae species native to North America over the years, and to the spread of invasive stink bugs throughout this region, in particular, the brown marmorated stink bug, (Halyomorpha halys). There is a lack of decision-making frameworks that provide more efficient sampling for stink bugs in soybean for this region, and there is a need to understand the dispersal capacities of laboratory-reared H. halys. Therefore, my research developed more efficient sampling for herbivorous stink bugs in this region and assessed the dispersal capacity of H. halys under laboratory conditions. First, I developed a binomial or decision-making sequential sampling plan for herbivorous stink bugs by using data from 11 states of the North Central Region. Results showed that using a tally threshold of 3 stink bugs per 25 sweeps for action thresholds corresponding to the current action thresholds of 5 (soybean grown for seeds) and 10 (soybean grown for grain) stink bugs per 25 sweeps, provided the best sampling outcomes in terms of efficiency and accuracy. In addition, we showed that 18 and 12 sample units, for action thresholds of 5 and 10 stink bugs per 25 sweeps respectively, would be needed for reliable decision-making sampling. The development of a binomial sequential sampling plan for stink bugs in soybean should provide increased efficiency with regards to the number of sample units required to reach a management decision. Secondly, I assessed the effects of starvation, age, mating status, and pre-flight weight on flight parameters of laboratory-reared H. halys using flight mills. Although some statistical differences were observed across the experiments, these differences represented minimum ecological significance. These results could reflect the resilience of H. halys as a successive invasive species to North America and could help predict the dispersal potential of this species in Minnesota. The results of my thesis will provide valuable information to fine-tune integrated pest management strategies for stink bugs in the North Central Region, enabling more efficient scouting for growers and consultants as well as better forecasting the dispersal capacity of an important invasive species to the region.Item Influence of eastern spruce dwarf mistletoe on stand structure and composition in northern Minnesota(Forest Ecology and Management, 2021) Skay, R.; Windmuller-Campione, M.A.; Russell, M.B.; Reuling, L.F.Black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) is one of the most common tree species in the boreal forest. However, there is limited information on one of the major disturbance agents, eastern spruce dwarf mistletoe (Arceuthobium pusillum Peck; EDM) a native, parasitic plant that influences stand development especially at the southwestern range limit of black spruce in Minnesota. The goal of our study was to quantify overstory and understory (sapling and seedling) structure and composition in productive black spruce stands across three EDM severity categories: uninfected (0% EDM), low (<50% of stand infected with EDM), and high (>50% of stand infected with EDM) across northern Minnesota during the summer of 2017. The presence of EDM infection in stands shifted species composition and structure compared to uninfected stands. Uninfected stands were dominated by black spruce in both overstory and understory and on average had a uni-modal diameter distribution. Both low and high EDM severity stands had significantly greater overstory species richness, Shannon’s diversity index, and Shannon’s Evenness compared to uninfected stands. However, stands with high EDM infections had the most black spruce infected with EDM in both the overstory and sapling layer, which will likely kill the infected trees within seventeen years and may result in a shifting in forest composition or a transition to non-forested conditions. The presence and severity of EDM influences stand structure and composition and subsequently stand development. Depending on the goals and objectives and ultimate desired future conditions both at the stand and the broader landscape level, natural resource managers may choose more or less intensive management of EDM.Item The effectiveness of using targeted grazing for vegetation management: a meta-analysis(Restoration Ecology, 2021) Marchetto, Katherine M.; Wolf, Tiffany M.; Larkin, Daniel J.The use of targeted grazing to control undesired plants as a component of ecological restoration is gaining in popularity, but there is considerable uncertainty among land managers about the effectiveness of this approach. We synthesized existing literature on the use of livestock (ruminants, swine, and equids) to control undesired plants using a meta‐analysis to address questions about the effectiveness of the approach. Seventy studies matched our inclusion criteria; these comprised 86% peer‐reviewed journal articles and 14% gray literature. Studies were conducted in 17 countries but highly concentrated in the United States and Europe. Cattle, goats, horses, and sheep were used for vegetation management in the studies. Most target plant species were nonnative perennial forbs. Median study duration was 3 years, with a maximum of 10 years. We found that, overall, the use of targeted grazing significantly reduced undesired plants and significantly increased plant species richness. However, several important questions remain. In particular, further research is needed to differentiate temporary defoliation from actual plant mortality, to separate the contributions of native versus nonnative species to gains in plant species richness, and to address longer term outcomes following grazing cessation.
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