Browsing by Subject "biological control"

Now showing 1 - 8 of 8
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    Biological control benefit-risk analysis; Heimpel et al. Ecological Applications
    (2024-05-06) Heimpel, George E; Abram, Paul K; Causton, Charlotte E; Celis, Sabrina L; Coll, Moshe; Hardy, Ian CW; Mangel, Marc; Mills, Nicholas J; Segoli, Michal; heimp001@umn.edu; Heimpel, George E; University of Minnesota Heimpel Laboratory
    The release of biological control agents has been an important means of controlling invasive species for over 150 years. While these releases have led to the sustainable control of over 250 invasive pest and weed species worldwide, a minority have caused environmental harm. A growing recognition of the risks of biological control led to a focus on risk assessment beginning in the 1990s along with a precipitous decline in releases. While this new focus greatly improved the safety of biological control, it came at the cost of lost opportunities to solve environmental problems associated with invasive species. A framework that incorporates benefits and risks of biological control is thus needed to understand the net environmental effects of biological control releases. We introduce such a framework, using native biodiversity as the common currency for both benefits and risks. The model is based on interactions among four categories of organisms: (i) the biological control agent, (ii) the invasive species (pest or weed) targeted by the agent, (iii) one or more native species that stand to benefit from the control of the target species, and (iv) one or more native species that are at risk of being harmed by the released biological control agent. Conservation values of the potentially benefited and harmed native species are incorporated as well, and they are weighted according to three axes: vulnerability to extinction, the ecosystem services provided, and cultural significance. Further, we incorporate the potential for indirect risks to native species, which we consider will result mainly from the ecological process of agent enrichment that may occur if the agent exploits but does not control the target pest or weed. We illustrate the use of this framework by retrospectively analyzing the release of the vedalia beetle, Novius (= Rodolia) cardinalis, to control the cottony cushion scale, Icerya purchasi, in the Galapagos Islands. While the framework is particularly adaptable to biological control releases in natural areas, it can also be used in managed settings, where biological control protects native species through the reduction of pesticide use.
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    European fruit lecanium (Parthenolecanium corni) occurrence in hybrid hazelnut plantings in Minnesota and associated parasitoid fauna from 2022
    (2023-07-27) Traband, Simone G; Aukema, Brian H; Luhman, John C; Shanovich, Hailey N; hnshanovich@gmail.com; Shanovich, Hailey N
    These data were collected in the summer of 2022 as an independent undergraduate research project at the University of Minnesota by Simone Traband (undergraduate student, class of '24) under the mentorship of Hailey Shanovich (graduate student, class of '23). The goals of the project were to collect preliminary data on 1) the abundance of a soft scale insect pest, European fruit lecanium (Parthenolecanium corni), on hybrid hazelnut plants (Corylus americana x Corylus avellana) in experimental plantings at the University of Minnesota research stations, and 2) the prevalence of biological control by Hymenopteran parasitoid wasps and an endoparasitic fungi (Ophiocordyceps clavulata). These data accompany the paper "Synopsis of biological control for European fruit lecanium (Parthenolecanium corni) by parasitoids in North America and preliminary findings in hybrid hazelnut orchards" by Traband et al. 2023 in the Great Lakes Entomologist. The preliminary field experiment was conducted at two experimental hybrid hazel plantings in Rosemount, Minnesota. Full details of study sites and other methodology can be found in the paper by Traband et al. 2023. On 11 July 2022 seven infested hazel plants were chosen to sample for scale insects from one hybrid hazelnut planting (n=7), and then on 22 July 2022 from two hybrid hazelnuts plantings (n = 4, n = 3) for a total of 14 plants. On each date, sampling of each plant was done for 15 person-minutes (i.e., three observers searching each plant for scales for five minutes), during which branches observed to contain one or more scale insects, no matter the status (i.e., showed signs of parasitism or not), were collected via hand pruners. Collected branches were immediately brought back to the lab and thoroughly examined to determine the number and status of every scale insect broken into three categories: showing signs of parasitism by fungus (i.e., fungal stromata protruding from scale insect), showing signs of parasitism by Hymenopteran parasitoids (i.e., containing a parasitoid exit hole in shell), or showing no signs of parasitism (i.e., showing no signs of parasitism). Branches containing scales showing no signs of parasitism were preserved for a duration of three weeks for purposes of parasitoid rearing and inspected every other day and any emerged parasitoids were collected and frozen until they could be identified. On 8 August 2022, all scale insects contained in jars were inspected for parasitoid exit holes, dissected to check for parasitoid larvae, pupae, or adults, and then discarded. All collected Hymenopteran parasitoid wasps were identified to the lowest taxonomic level possible.
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    Evaluating biological control of the soybean gall midge (Resseliella maxima GagnƩ) in Minnesota
    (2023-12) Melotto, Gloria
    The soybean gall midge, Resseliella maxima GagnƩ (Diptera: Cecidomyiidae), poses a threat to soybean crops in the Midwest US. However, little is known regarding its natural enemies and the potential for biological control. Therefore, this thesis aims to fill this knowledge gap by focusing on evaluating biological control for R. maxima. To achieve this, we conducted a two-year survey to investigate the parasitoid and predator communities associated with R. maxima infestations in Minnesota. Our findings confirmed parasitism of R. maxima larvae by the wasp Synopeas maximum Awad & Talamas (Hymenoptera: Platygastridae) and examined the spatial-temporal dynamics of parasitism within fields. Additionally, our observations showed that the predator Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) was the most prevalent species in the soybean fields in this study, presented temporal overlap with the pest, and had a high propensity to feed on R. maxima larvae. We concluded that further research should evaluate how parasitism rates by S. maximum could be promoted in production fields and that Pt. melanarius should receive further attention as a potential biological control agent of R. maxima.
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    Expanded Use of Hail Netting in Minnesota Apple: Impacts on Insect Pests, Fruit Production, and Natural Enemies
    (2023-08) Nelson, Sally
    The management of apple insect pests in orchards in the United States has historically depended upon broad-spectrum insecticides. Exclusion netting has begun to be adopted by fruit growers across the world to assist with the management of insect pests and to reduce chemical input. In apple, the first exclusion netting system was developed in the early 2000s, and new developments in color, mesh size, and material continue to be made. Hail netting, originally developed to protect pome fruit from hail damage, has begun to be adopted by growers in Minnesota, USA. The potential for hail netting to be used as a dual-purpose management tool, both to protect from hail and exclude key insect pests in Minnesota, is investigated in this study. This research examined the efficacy of hail netting as a pest exclusion tactic and the non-target effects of hail netting on fruit production and the natural enemy community. First, the efficacy of hail netting in reducing pest populations was compared to a commercial growerā€™s spray schedule in Minnesota. The insecticides used by the grower in 2021 and 2022 were clothianidin, abamectin, novaluron, and acetamiprid. The three insect pests that we monitored for were the codling moth (Cydia pomonella Linnaeus; Lepidoptera: Tortricidae), the apple maggot (Rhagoletis pomonella Walsh; Diptera: Tephritidae), and the red-banded leafroller (Argyrotaenia velutinana Walker; Lepidoptera: Tortricidae). This work was conducted as a two-year field study, with both years showing a significant reduction in pest pressure under the netting. Insecticide application did not significantly reduce pest pressure from any of the three pests. The interaction of netting and insecticide application was found to significantly improve fruit quality at harvest time. Neither netting nor insecticide was found to significantly influence apple yield. Second, hail netting significantly reduced predator family richness and the number of individuals that were caught. The most abundant predator family observed was Anthocoridae, along with Coccinellidae, Formicidae, and Empididae. All of these families were significantly reduced in number inside the netting. The diversity of predator families, evaluated using Simpsonā€™s and Shannonā€™s diversity indices, was not significantly influenced by the netting or spray treatments. Spray treatments did not significantly reduce the family richness or the number of individual predators caught in any family. The environmental risk of the insecticides used in this study was evaluated using the Environmental Impact Quotient and the Pesticide Risk Tool. The tools had slightly different findings, but overall there was a higher risk to non-target arthropods caused by the neonicotinoids clothianidin and acetamiprid.
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    Integrating chemical and biological controls for management of soybean aphid
    (2016-11) Tran, Anh
    The soybean aphid, Aphis glycines Matsumura, is predominately managed by foliar application of broad-spectrum insecticides. Though broad-spectrum insecticides can provide immediate therapeutic control of A. glycines, the insecticides can negatively impact natural enemies. Natural enemies of A. glycines are important for suppressing aphid population. However, natural enemies are not integrated with A. glycines management. Within this thesis, I examine the ability of a new selective insecticide to suppress A. glycines population and conserve natural enemies. I also develop a sampling plan that can estimate natural enemy populations with a desired level of precision. The results from these studies will provide information on how to better integrate natural enemies into current A. glycines management programs.
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    Population Ecology Of Aphelinus Certus, An Adventive Parasitoid Of Soybean Aphid In North America, With Implications For Biological Control
    (2020-05) Miksanek, James
    Parasitoids 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 dāˆ’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 2017ā€“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.
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    Risk and efficacy in biological control: an evaluation of the aphid parasitoid Aphelinus certus in North America
    (2016-09) Kaser, Joseph
    Invasive species are causing increasing harm to native biodiversity, ecosystems, agriculture, and other natural resources. Classical biological control is a powerful and cost-effective strategy for long-term invasive species management. However, while importation of biological control agents has many potential benefits, it also entails risks, such as harm to non-target native species. Therefore, candidate biological control agents are studied prior to release to predict their safety. Little is known, however, about how traits affecting the safety of biological control agents may also impact their efficacy in terms of reducing invasive pest populations. In this dissertation, I investigate the interacting causes and consequences of risk and efficacy in biological control. I approach this investigation first from a theoretical standpoint, including a literature review and a mathematical modeling framework. I then investigate the aphid parasitoid Aphelinus certus Yasnosh (Hymenoptera: Aphelinidae) which attacks the invasive soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). In the early 2000s, Aphe. certus was evaluated as a potential classical biological control agent of the soybean aphid, but it was precluded from release due to concerns over ecological safety. However, the parasitoid was accidentally introduced anyway, and thus provides an interesting case study to evaluate the causes of and consequences of biological control risk and efficacy. Chapter 1 of this dissertation provides a literature review and synthesis of the potential impacts of natural enemy-mediated indirect effects on both risk and efficacy in biological control. Polyphagous natural enemies cause various indirect interactions between their prey/host populations. These indirect interactions may be reciprocally negative (i.e. apparent competition), but can be any combination of positive, negative, or neutral. I focus on parasitoids to illustrate the importance of natural enemy-mediated indirect interactions in biological control risk-benefit assessment. In Chapter 2, I utilize a mathematical modeling framework to investigate direct and indirect interactions between a generalized biological control agent, and its target and non-target hosts. I use Nicholoson-Bailey form difference equations to simulate a one-parasitoid two-host system, and I evaluate conditions under which biological control safety and efficacy interact. Apparent competition can have important benefits for increasing biological control efficacy, even at low levels of non-target impact. However, under conditions of parasitoid egg limitation, high attack rates on resistant non-target hosts can dramatically decrease biological control efficacy while concurrently increasing non-target risk. These findings are discussed in the context of biological control agent pre-release risk-benefit assessment. The code for an interactive application of this model is provided as supplementary material for Chapter 2, and is presented in the Appendix. In Chapter 3, I investigate the potential for perennial biofuel plantings to enhance biological control of the soybean aphid by parasitoids. Cultivated biofuels provide an important source of renewable energy, and may provide additional ecosystem services, such as enhanced natural enemy communities and increased biological control of pests in neighboring crops. I conducted a large-scale randomized experiment to test for effects of biofuel plantings on biological control of the soybean aphid in surrounding soybean fields. There was no significant effect of any biofuel treatment on the parasitoid community or on soybean aphid density compared to controls. However, the experiment coincidentally captured the early colonization stages of the introduced aphid parasitoid A. certus in Minnesota. Aphelinus certus is increasing in density in Minnesota soybean fields, and this increase corresponds with a decrease of resident Aphidiinae parasitoids over a three-year period. In Chapter 4, I present an evaluation of the host range of A. certus. I exposed A. certus to 17 species of aphid hosts in no-choice tests. Aphelinus certus attacked most species presented to it, but mummification rates and adult emergence were highly variable. I mapped host use data onto an aphid phylogeny to see if host phylogeny predicted host use. Aphelinus certus mummification significantly clustered with host relatedness (P=0.043). Several native aphid species are shown to be at risk of attack by A. certus. Additionally, several pest aphid species present in North America may also be subjected to biological control by A. certus. In Chapter 5, I evaluate the biological control impact of A. certus on the soybean aphid. The observed increase of A. certus prevalence in North American cultivated soybeans does not necessarily indicate that the parasitoid is substantially contributing to soybean aphid biological control. I conducted an exclusion-cage experiment designed to isolate the impact of parasitoids compared to other resident natural enemies of the soybean aphid. I found that A. certus greatly outnumbered all other soybean aphid parasitoids, and that it significantly reduced soybean aphid populations over a time span of less than two weeks compared to controls (P<0.0001). Moreover, parasitoids alone resulted in aphid densities that were statistically equivalent to the combined effect of predators and parasitoids (P=0.95). These results indicate that A. certus is an important new component of the soybean aphid natural enemy community in North America. Aphelinus certus provides an informative example of a biological control agent that is effective but also risky in terms of non-target impact to native species.