MITPPC Research publications
Persistent link for this collectionhttps://hdl.handle.net/11299/241449
Browse
Browsing MITPPC Research publications by Title
Now showing 1 - 20 of 50
- Results Per Page
- Sort Options
Item Aecial and telial host specificity of Puccinia coronata var. coronata, a Eurasian crown rust fungus of two highly invasive wetland species in North America(Plant Disease, 2023-08) Greatens, Nicholas; Jin, Yue; Pablo, D. OliveraThe Eurasian crown rust fungus Puccinia coronata var. coronata (Pcc) was recently reported in North America and is widespread across the Midwest and Northeast United States. Pcc is a close relative of major pathogens of oats, barley, and turfgrasses. It infects two highly invasive wetland plants, glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea) and could be useful as an augmentative biological control agent. We conducted large greenhouse trials to assess the host specificity of Pcc and determine any threat to cultivated cereals, turfgrasses, or native North American species. A total of 1,830 accessions of cereal crop species and 783 accessions of 110 other gramineous species were evaluated. Young plants were first inoculated with a composite uredinial inoculum derived from aecia. Accessions showing sporulation were further tested with pure urediniospore isolates. Sixteen potential aecial hosts in the families Rhamnaceae and Elaeagnaceae were tested for susceptibility through inoculation with germinating teliospores. Thirteen grass species within five genera in the tribe Poeae, Apera, Calamagrostis, Lamarckia, Phalaris and Puccinellia, and four species in Rhamnaceae, Frangula alnus, F. californica, F. caroliniana and Rhamnus lanceolata, were found to be susceptible to Pcc, with some species native to North America. All assessed crop species and turfgrasses were resistant. Limited sporulation, however, was observed on some resistant species within Poeae and four other tribes, Brachypodieae, Bromeae, Meliceae, and Triticeae. Among these species are oats, barley, and Brachypodium distachyon, suggesting the possible use of Pcc in studies of non-host resistance.Item Can Co-Grazing Waterfowl Reduce Brainworm Risk for Goats Browsing in Natural Areas?(EcoHealth, 2022) Marchetto, Katherine M.; Linn, Morgan M.; Larkin, Daniel J.; Wolf, Tiffany M.Goats browsing in woodlands, whether for livestock production goals or vegetation management (e.g., targeted grazing to control invasive plants), are at risk of meningeal worm ( Parelaphostrongylus tenuis ) infection. Indeed, up to 25% incidence has been observed in goats employed in vegetation management. Infection, which occurs via the consumption of an infected gastropod intermediate host, is potentially deadly in goats. We experimentally tested whether co-grazing with waterfowl could reduce goats’ exposure via waterfowl consumption of gastropods. Gastropods were sampled in a deciduous woodland before and after the addition of goats alone, goats and waterfowl, or a control with no animal addition. We found that goats browsing on their own increased the abundance of P. tenuis intermediate hosts; however, when goats co-grazed with waterfowl, these increases were not observed. Importantly, waterfowl did not significantly affect overall gastropod abundance, richness, or diversity. Thus, waterfowl co-grazing may effectively reduce goat contact with infectious gastropods without detrimentally affecting the gastropod community. While co-grazing goats with waterfowl may decrease their P. tenuis exposure risk, additional research is needed to confirm whether waterfowl can actually lower P. tenuis incidence.Item Cold tolerance and overwintering survival of Aphelinus certus (Hymenoptera: Aphelinidae), a parasitoid of the soybean aphid (Hemiptera: Aphididae) in North America(Bulletin of Entomological Research, 2023-06) Stenoien, Carl M.; Christianson, Lindsey; Welch, Kelton; Dregni, Jonathan; Hopper, Keith R.; Heimpel, George E.Broad-spectrum insecticides are the main control measure of the invasive and economically damaging soybean aphid (Aphis glycines) in North America, although biological control by resident natural enemies can also greatly diminish population levels. One such natural enemy is the accidentally introduced Eurasian parasitoid Aphelinus certus (Hymenoptera: Aphelinidae), though its impact appears to be limited by low rates of parasitism early in the growing season. We tested the hypothesis that A. certus might experience high overwintering mortality. In the laboratory, we used thermocouple thermometry to measure the supercooling points of diapausing parasitoids and assessed parasitoid survival after exposure to ecologically relevant durations of low temperature. We found A. certus to be freeze-intolerant with a median supercooling point of -28 & DEG;C. When exposed to temperatures of 0 & DEG;C for up to 7 months, adults emerged only after exposures of at least 60 days and survival decreased with durations beyond 150 days. We also conducted in-field studies at sites from northern Minnesota to southern Iowa to determine if diapausing A. certus could overwinter above and below the snowpack. Survival was negatively correlated with increasing latitude and was greater for parasitoids placed on the ground than 1 meter off the ground, likely due to the warmer and stabler temperatures of the subnivean microclimate. Our results suggest that A. certus is capable of overwintering in the region inhabited by soybean aphid but may experience substantial mortality even under ideal conditions. Climate change is predicted to bring warmer, drier winters to the North American Midwest, with decreased depth and duration of snow cover, which may further reduce overwintering survival.Item Colonization and reproduction of potential competitors with mountain pine beetle in baited logs of a new host for mountain pine beetle, jack pine(Forest Ecology and Management, 2021-10) Smith, Zach M.; Chase, Kevin D.; Takagi, Esturo; Kees, Aubree M.; Aukema, Brian H.The mountain pine beetle (Dendroctonus ponderosae Hopkins) is a bark beetle that is native to pine forests of western North America and the Black Hills of South Dakota. Recent eastward range expansion into stands of jack pine (Pinus banksiana) and associated hybrids with lodgepole pine (Pinus contorta) in western Canada has created concern that the insect will continue moving eastward. In the Great Lakes region, mountain pine beetle would encounter novel species of pines and associated insect fauna; interactions with which are largely unexplored. We baited logs of jack pine with lures for mountain pine beetle and Ips grandicollis (Eichhoff) alone and in combination in a 2 × 2 factorial design in the Black Hills of South Dakota. Both insects occur in this region, but not jack pine, a common species in the Great Lakes region of North America at risk of invasion by mountain pine beetle. We measured attraction and reproduction of insects that colonized the logs. Ips grandicollis were significantly more attracted to logs of jack pine baited with their aggregation pheromone, ipsenol, than unbaited logs or those baited with pheromones of mountain pine beetle and myrcene, a host volatile. Colonization by I. grandicollis was inhibited by the presence of lures for mountain pine beetle. We also found larvae of longhorn borers, likely Monochamus spp., infesting logs. These borers, which act as competitors and facultative predators of bark beetles, were significantly attracted to logs baited with ipsenol over those baited with lures for mountain pine beetle. Our results suggest that if mountain pine beetle were to invade the Great Lakes Region, common bark and wood-boring species such as I. grandicollis and longhorn borers would not compete with mountain pine beetles at tree-colonizing stages, and thus could pose little resistance to invasion.Item Defensive response of evolutionarily naïve Pinus sylvestris to the mountain pine beetle fungal associate Grosmannia clavigera in comparison to Pinus ponderosa(Forest Ecology and Management, 2023-10) Chase, Kevin D.; Rynders, Kathryn J.; Maddox, Mitchell P.; Aukema, Brian H.Mountain pine beetle (MPB, Dendroctonus ponderosae) is a destructive pest of pine forests in western North America. This insect is currently expanding its range across the Canadian boreal forest towards eastern North America, where a suite of novel pine species will be encountered. One species of pine without prior association with MPB is Pinus sylvestris (Scots pine), which is native to Europe and naturalized in parts of central and eastern North America. Here, we take advantage of a unique opportunity in the Black Hills of South Dakota where an isolated, planted, and mature stand of P. sylvestris and native Pinus ponderosa (ponderosa pine) co-exist within the range of MPB. We conducted a punch-inoculation experiment to determine the chemical response of P. sylvestris from a blue-stain fungus associated with MPB, Grosmannia clavigera, and compared the response to that of P. ponderosa. We found that P. sylvestris had a higher localized monoterpene response than P. ponderosa in response to inoculation, but a lower sesquiterpene response. Among the significant monoterpenes associated with MPB behavior, limonene, 3-carene, and myrcene had a larger localized response in P. sylvestris than P. ponderosa; lower levels of 4-allylanisole were found in P. sylvestris. Fungal inoculation did not induce a stronger terpenoid response than mechanical wounding without inoculation, indicating that P. sylvestris responds to mechanical damage similarly as to fungal inoculation. Pinus sylvestris may provide one alternative plantation species for timber production in the Great Lakes Region following mountain pine beetle incursion, however, more evaluation is needed to determine the role of this species in future plantings.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 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 Distribution and Traits of the Fungal Pathogen Fusarium virguliforme that Influence Spread and Survival in Minnesota(2021-08) Hall, RebeccaFusarium virguliforme is an invasive fungal pathogen responsible for soybean sudden death syndrome (SDS) and root rot of other legumes. Despite a previous study that suggested the pathogen would not survive in Minnesota due to winter cold stress, the pathogen was found in southern Minnesota in 2002 and has continued to spread throughout the state since its discovery. While much has been learned about the SDS pathogen in the United States, more work is needed to better understand the distribution of F. virguliforme in soybean and other crop fields and the strategies the pathogen uses to survive and spread in northern climates. This thesis includes studies of key traits that may aid in the survival of F. virguliforme, including 1) the asymptomatic and symptomatic host range of this fungus in a field setting, 2) the cold temperature limits of the pathogen’s survival, and 3) the unique nutrient use profiles of F. virguliforme. This work sought to expand our knowledge of the distribution of the pathogen within Minnesota. A distribution study in soybean fields was conducted in 2018 and 2019 based on SDS symptoms and the use of a specific qPCR assay. SDS and F. virguliforme were confirmed for the first time in Rice, Isanti, and Stevens counties; and the pathogen was confirmed for the first time in Clay, Douglas, Hubbard, and Pope counties. Cold temperature limits of the pathogen that may influence the spread and survival of F. virguliforme in Minnesota’s current and future climate were explored. It was determined that the pathogen can survive to temperatures of -40°C and thus survival is not likely limited by cold temperatures in Minnesota. The host range of the pathogen was studied to define which plant species may be vulnerable to disease development and potentially help the survival of F. virguliforme. Eleven species of dry edible beans, native legumes, prairie grasses, and prairie flowers common in the Midwestern United States were selected for field and greenhouse studies. It was determined that black bean, pinto bean, kidney bean, and pea are symptomatic hosts, whereas alfalfa, showy tick trefoil, black-eyed Susan, Indiangrass, partridge pea, and white clover are asymptomatic hosts. Lastly, the nutrients that support the growth of F. virguliforme, as well as the relative nutrient preferences and competitive abilities of F. virguliforme compared to other fungal and oomycete species commonly found in soil or soybean roots was explored within this thesis. The results suggest that F. virguliforme utilizes a larger number of carbon and nitrogen sources, both of which are potentially released from germinating seeds and crop residue and are strong stimulants of F. virguliforme growth. Additionally, it was determined that F. virguliforme is more competitive for these nutrients than the other species included in this study.Item Economic-threshold-based classification of soybean aphid, Aphis glycines, infestations in commercial soybean fields using Sentinel-2 satellite data(Crop Protection, 2023-12) Ribeiro, Arthur V.; Lacerda, Lorena N.; Windmuller-Campione, Marcella A.; Cira, Theresa M.; Marston, Zachary P.D.; Alves, Tavvs M.; Hodgson, Erin W.; MacRae, Ian V.; Mulla, David J.; Koch, Robert L.The soybean aphid (SBA), Aphis glycines Matsumura (Hemiptera: Aphididae), is a significant insect pest of soybean, Glycine max (L.) Merrill (Fabales: Fabaceae), and field treatment decisions for this pest are based on average field populations. Previous studies indicated that ground- and drone-based red-edge and near-infrared remote sensing can be used to detect plant stress caused by SBA infestations in soybean. However, it remains to be determined if remote sensing for SBA can be expanded to field or landscape scale using satellite-based platforms. Thus, this research was conducted in three steps to determine the potential of using Sentinel-2 satellite data for the classification of SBA infestations in soybean fields using simulated and actual Sentinel-2 satellite spectral reflectance. In the first step, as a proof of concept, hyperspectral data from cage studies were used to simulate Sentinel-2 bands and vegetation indices (VIs), conducted in nine trials at multiple locations between 2013 and 2021. The effects of SBA from caged plants on simulated data were evaluated with random intercept linear mixed models. The satellite simulation indicated a significant effect of SBA on the spectral reflectance of caged soybean plants (p < 0.05) for four satellite bands (5, 6, 7, and 8A) and five VIs (NDVI, GNDVI, SAVI, OSAVI, and NDRE). In the second step, actual Sentinel-2 spectral reflectance and corresponding aphid counts of commercial soybean fields, collected from 2017 to 2019, were obtained. The relationship between SBA counts and Sentinel-2 spectral reflectance from commercial soybean fields were evaluated with general linear models. A significant effect of SBA was observed for three satellite bands (6, 7, and 8A) and three VIs (NDVI, SAVI, and OSAVI). In the third step, linear support vector machine (LSVM) models for the classification of SBA infestations as above or below a previously determined economic threshold of 250 aphids per plant were developed using simulated Sentinel-2 bands and VIs from the caged plots, and were tested on actual Sentinel-2 data from commercial soybean fields. The best LSVM model for the classification of aphids in soybean reached 91% accuracy, 85.7% sensitivity, and 93.3% specificity. Thus, simulations with caged plots can be used as an indication of the potential of using satellite data for the detection of plant stresses on a larger scale. Furthermore, this study advances decision-making for SBA, and the developed LSVM model can be used to update regional and local monitoring for the management of SBA.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.Item Effects of systemic insecticides against emerald ash borer on ash seed resources(Forest Ecology and Management, 2022-05) Mwangola, Dorah M.; Kees, Aubree M.; Grosman, Donald M.; Aukema, Brian H.Emerald ash borer (EAB), Agrilus planipennsis, is an invasive insect that was accidentally introduced to North America from Asia. It continues to spread rapidly across North America and is responsible for the death of tens of millions of ash trees (Fraxinus spp.). All North American species of ash are susceptible to EAB infestation threatening the ash resource and diversity. Measures such as systemic insecticide treatments in urban forests and collection of ash seeds provide a means of conserving genetic resources. Understanding the effect these insecticides could have on ash seed viability is therefore important to informing conservation efforts. Another potential concern for effective conservation of ash seeds is the ash seed weevil (Lignyodes spp.) whose larvae develop in and feed on ash seeds. However, the effect of EAB insecticides on weevil infestation levels in ash seeds has not been investigated to date. Our study investigated the effect of two systemic insecticide treatments, azadirachtin and emamectin benzoate, on levels of ash seed weevil infestation, seed germination ability, and seed germination time of seeds collected from boulevard trees of green ash (F. pennsylvanica Marsh.) in cities in Minnesota from 2017 to 2019. Weevil infestation levels were similar between untreated and treated trees in 2017 and 2018. In 2019, the weevil prevalence in untreated trees was on average 17% and 30% higher than in azadirachtin and emamectin benzoate-treated trees respectively. Weevil infestation data suggests that repeated insecticide treatments at labelled rates can reduce seed weevils that target germplasm. Additionally, insecticide treatments did not affect ash seed germination rates between treatments. These results suggest that systemic insecticides may be effective at conserving the seed resource in addition to known benefits such as canopy preservation.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 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 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 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 Genetic Diversity and Aggressiveness of Fusarium virguliforme Isolates Across the Midwestern United States(Phytopathology, 2022) Olarte, Rodrigo A.; Hall, Rebecca; Tabima, Javier F.; Malvick, Dean; Bushley, KathrynSudden death syndrome (SDS) of soybean is a damaging disease caused by the fungus Fusarium virguliforme. Since this pathogen was first reported in the southern U.S. state of Arkansas in 1971, it has spread throughout the midwestern United States. The SDS pathogen primarily colonizes roots but also produces toxins that translocate to and damage leaves. Previous studies have detected little to no genetic differentiation among isolates, suggesting F. virguliforme in North America has limited genetic diversity and a clonal population structure. Yet, isolates vary in virulence to roots and leaves. We characterized a set of F. virguliforme isolates from the midwestern United States, representing a south to north latitudinal gradient from Arkansas to Minnesota. Ten previously tested microsatellite loci were used to genotype isolates, and plant assays were conducted to assess virulence. Three distinct population clusters were differentiated across isolates. Although isolates ranged in virulence classes from low to very high, little correlation was found between virulence phenotype and cluster membership. Similarly, population structure and geographic location were not highly correlated. However, the earliest diverging cluster had the lowest genetic diversity and was detected only in southern states, whereas the two other clusters were distributed across the Midwest and were predominant in Minnesota. One of the midwestern clusters had the greatest genetic diversity and was found along the northern edge of the known distribution. The results support three genetically distinct population clusters of F. virguliforme in the United States, with two clusters contributing most to spread of this fungus across the Midwest.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 The Impact of Systematic Insecticides Against Emerald Ash Borer on Phenology of Urban Ash Trees(Journal of Economic Entomology, 2023-02) Mwangola, Dorah M.; Kees, Aubree M.; Grosman, Donald M.; Aukema, Brian H.The continued threat of emerald ash borer (Agrilus planipennis; EAB) to North American ash trees (Fraxinus spp.) has necessitated the use of systemic insecticide treatments as a primary control strategy against EAB in urban centers. Altered tree phenology due to systemic insecticides could mediate nontarget effects on other insect species, such as seed weevils or leaf-feeders, but whether such injections alter phenological events has not been studied.This study assessed the effects of systemic injections of emamectin benzoate or azadirachtin relative to untreated controls on the spring and fall phenology of mature green ash trees in Saint Paul, MN, USA from fall 2017 to spring 2019. EAB was first detected in this area in 2009.Trees showed minor, visible signs of EAB infestation at study initiation, but not mortality. We examined six phenological events: bud swelling, budburst, flowering, leaf out, leaf color change, and leaf abscission using a visual survey protocol.The timing of phenological events was similar across the different treatments for all but two of events; budburst and flowering. Budburst and flowering occurred 7 d and 5 d earlier, respectively, in treated trees than untreated trees. Given symptoms observed, we posit that delays in these events in untreated trees were due to infestations of EAB and the treatments of emamectin benzoate or azadiractin simply preserved the original phenology.The results from this study suggest that systemic insecticides may mitigate changes in ash tree phenology such as delayed leaf out that may be early symptoms of emerald ash borer.Item Improving predictions of range expansion for invasive species using joint species distribution models and surrogate co-occurring species(Journal of biogeography, 2021-02) Briscoe Runquist, Ryan D.; Lake, Thomas A.; Moeller, David A.Aims Species distribution models (SDMs) are often used to forecast potential distributions of important invasive or rare species. However, situations where models could be the most valuable ecologically or economically, such as for predicting invasion risk, often pose the greatest challenges to SDM building. These challenges include non‐equilibrium range expansion, low or uneven prevalence, and projecting distributions into environments that are non‐analogous to the environments used for model building. Location Minnesota, USA. Taxon Cardamine impatiens (Narrowleaf Bittercress), Celastrus orbiculatus (Oriental Bittersweet), and Humulus japonicus (Japanese Hops). Methods We took a novel approach to build robust species distribution models of invasive species using occurrence‐environment correlations between invasive species and co‐occurring native community members. The correlations were obtained from a joint species distribution model (JSDM) of a densely sampled database of 10,336 MN plant communities from across the state of Minnesota, USA. Positively and negatively associated native species were incorporated into the model as surrogate presences and pseudoabsences (weighted by their environmental correlations) along with invasive species occurrences records (surrogate SDMs). Results Surrogate models performed better than traditional SDMs in predicting occurrences along the northern invasion margin (outside the training area). Both types of models had similarly high cross‐validation metrics in the area of training. Surrogate models also predicted greater range expansion beyond the current geographic range. Main conclusions These results demonstrate that modelers can take advantage of detailed community data to develop SDMs that leverage surrogate native species as phytometers of environments beyond the current area of occupancy. The additional information in surrogate models generates highly effective predictions of invasive species along expanding range margins.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.
- «
- 1 (current)
- 2
- 3
- »