132 research outputs found
Balancing Disturbance and Conservation in Agroecosystems to Improve Biological Control
No full textDisturbances associated with agricultural intensification reduce our ability to achieve sustainable crop production. These disturbances stem from crop-management tactics and can leave crop fields more vulnerable to insect outbreaks, in part because natural-enemy communities often tend to be more susceptible to disturbance than herbivorous pests. Recent research has explored practices that conserve natural-enemy communities and reduce pest outbreaks, revealing that different components of agroecosystems can influence natural-enemy populations. In this review, we consider a range of disturbances that influence pest control provided by natural enemies and how conservation practices can mitigate or counteract disturbance. We use four case studies to illustrate how conservation and disturbance mitigation increase the potential for biological 2 control and provide co-benefits for the broader agroecosystem. To facilitate the adoption of conservation practices that improve top-down control across significant areas of the landscape, they will need to provide multifunctional benefits, but should be implemented with natural enemies explicitly in mind.This is a manuscript of an article published as Tooker, John F., Matthew E. O'Neal, and Cesar Rodriguez-Saona. "Balancing disturbance and conservation in agroecosystems to improve biological control." Annual Review of Entomology 65 (2020): 81-100. doi: 10.1146/annurev-ento-011019-025143. Posted with permission.</p
Local and regional approaches to studying the phenology and biological control of the soybean aphid
No full textSoybean aphids Aphis glycines Matsumura (Hemiptera: Aphididae) are an economic pest of soybean Glycine max (L.) Merr. in much of the United States and parts of Canada. Some crucial phenological information of A. glycines is unknown, specifically source-sink dynamics between and within host plants and factors guiding aphid migrations. In addition, there are discrepancies in the literature on the importance of food webs and how local landscape effects can alter A. glycines populations. Increasing our understanding of A. glycines population dynamics may improve predictions of aphid outbreaks and integrated pest management efforts. The first objective was to determine how landscape composition and heterogeneity impact A. glycines and their natural predator community. This study was centered in and around the Neal Smith National Wildlife Refuge located in Jasper County, Iowa. A second objective was to determine how prairie plantings adjacent to soybean impact A. glycines and natural enemy populations. To accomplish this, four study sites in central Iowa, transects were established up to 200 m in both soybean and prairie. A third objective was to describe A. glycines movement patterns on a regional scale. We monitored winged aphids (alates) using a suction trap network established at 42 locations over 10 states. Alates where correlated with northern latitudes which led to the last objective which was to predict A. glycines using low temperature data from the Midwest US and determine whether temperatures have reached A. glycines supercooling point (-34oC).</p
Development of integrated pest management techniques: Insect pest management on soybean
No full textThis dissertation is organized into six chapters. Chapter one contains a general introduction, including a review of the literature on the biology, damage caused, and control of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). In addition to soybean aphid biology and management, this chapter will also include a review of integrated pest management (IPM) theory including plant injury responses and insect threshold development. The chapters reporting the original research conducted through the course of study will progress from the applied to the basic: Chapter two will detail the effects of insecticide application techniques on soybean aphid management. Chapter three will report on the applicability of the current soybean aphid threshold on soybean grown in narrow-rows. Chapter four will compare the economic probability of net profit comparing preventive soybean aphid management programs to IPM. Chapter five will detail several soybean yield response models to two common sources of injury (e.g. assimilate removal and defoliation). Chapter five will also discuss how assimilate removal and defoliation interact in a common yield loss model, and how this information could aid in the development of comprehensive soybean aphid thresholds. Finally, chapter six will provide a brief overview of the conclusions of this original research and is followed by an acknowledgments section.</p
Beyond biotypes: Aphis glycines (Hemiptera: Aphididae) biology and the durability of aphid-resistant soybean
No full textIn North America, Aphis glycines, is capable of reducing soybean yields by as much as 40%. The management of A. glycines has relied heavily on the use of broad-spectrum insecticides that can be detrimental to both the pest and natural enemies that are present in soybean at the time of application. An alternative management strategy for A. glycines is the use of aphid-resistant soybean that contain Rag genes. The presence of three virulent A. glycines biotypes (i.e., able to overcome aphid-resistance genes) in the US however raises the question about the durability and practicality of Rag genes. Here I examined the potential interactions that may be occurring between both virulent and avirulent A. glycines on soybean, and whether fitness costs exist for virulent biotypes. I also evaluated whether the use of an interspersed refuge strategy for resistant and susceptible soybean would manage A. glycines populations, and determined their impact on natural enemies present in soybean. Our results demonstrate that a virulent A. glycines biotype is capable of obviating the resistance gene in soybean; therefore, making the plant a suitable host for both an avirulent and virulent biotype. This effect occurs in the absence of the virulent biotype for up to a period of five days. Fitness costs were present for all virulent biotypes that have been discovered. An interspersed refuge strategy reduces A. glycines populations, and has minimal impacts on natural enemies present in soybean. Future research will need to investigate the mechanism responsible for the obviation of resistance effect. Work should also be conducted to determine the durability of Rag genes when a refuge in a bag approach is used.</p
Development of best-practices for conserving beneficial insects within Iowa's agricultural landscape
No full textThe annual value of crop pollination and biological control of plant pests provided by beneficial insects is estimated to be worth at least $22 billion to United States crop production. Beneficial insects that supply these services to agricultural lands are threatened by limited or suboptimal resources due to the loss of biodiversity in agroecosystems, which is a growing concern in agricultural states like Iowa. Conservation practices are recommended to address a multitude of conservation concerns related to Iowa's declining natural resources; however, guidelines for best practices that conserve beneficial insects are not well defined. Due to the valuable relationship of beneficial insects and successful crop production, there is a need for developing best practices that conserve beneficial insects within Iowa's agricultural landscape. The first objective was to design mixtures of native perennial plants that range in diversity and resource availability and evaluate these different plant communities as candidates for buffer strips that attract and conserve beneficial insects. The second objective was to evaluate the insect community in non-crop buffer strips already established on organic farms and in the adjacent organic crops and conventional row crops. This research seeks to identify mixtures of native perennial plants optimized with resources attractive to pollinators and natural enemies and to determine if these mixtures can enhance Iowa's buffer strips to conserve beneficial insects and protect their services. Best-practices for conserving beneficial insects can be adapted for different regions, land uses, and habitat restoration scenarios beyond the study system used for this research.</p
Integrating soybean aphid and soybean cyst nematode management
No full textSoybean aphid, Aphis glycines, and soybean cyst nematode (SCN), Heterodera glycines, can interact through the soybean plant resulting in increased SCN reproduction on both SCN-resistant and SCN-susceptible varieties. The management of SCN is heavily reliant on the planting of PI 88788-derived SCN-resistant varieties to limit yield loss to SCN in the current year and future years. Virulence to PI 88788 is increasing in SCN field populations due to its extensive use. Therefore, it is increasingly important to manage any factor that increases SCN reproduction on SCN-resistant varieties. Here I examined management tactics including host-plant resistance and insecticidal seed treatments to limit soybean aphid populations and disrupt the interaction between soybean aphids and SCN. Neither host-plant resistance incorporating a single resistance gene nor insecticidal seed treatments were able to prevent yield loss from soybean aphids. Furthermore, host-plant resistance incorporating a single resistance gene also failed to disrupt soybean aphid-SCN interactions. Host-plant resistance incorporating a pyramid of two resistance genes was, however capable of limiting yield loss to soybean aphids. The pyramid line also limited aphid population densities to below levels where we would expect to observe soybean aphid-SCN interactions. Future research will need to investigate the ability of a pyramid line to disrupt soybean aphid-SCN interactions in the field and the potential consequences for yield and long-term sustainable SCN population management.</p
Classical and conservation biological control of pest insects within prairie and crop systems
No full textThe manipulation of beneficial insects can be done through purposeful releases of biological control organisms, or through manipulation of non-crop habitat. Both mechanisms are explored in various agroecosystems. In chapter 2, I determine if the parasitoid waspBinodoxys communis, imported from China, is able to colonize, and suppress soybean aphid, Aphis glycines in Iowa soybean fields. In addition, the effects of initial soybean aphid densities are measured. Binodoxys communis successfully colonized soybean aphids in Iowa soybean fields, but is not always effective at suppressing soybean aphid populations. Abiotic and biotic factors were more important for the suppression of soybean aphid. In addition, Binodoxys communis acts in a density-dependent manner when soybean aphid populations are lower. Thus, augmentative releases when soybean aphid populations are lower may limit soybean aphid populations. In chapter 3, I examined conservation of natural enemies (and other arthropod guilds) as part of a larger interdisciplinary study. Prairie vegetative strips were planted in various treatment amounts (0% to 20%), and distributions (0 to 3 strips) within watershed catchments devoted to annual crop production. Arthropods were significantly more abundant within prairie land cover than crop, but the various treatments had no effect on arthropod abundance. When examining the most commonly collected natural enemy taxa, we find that most taxa are more abundant within prairie over the entire season. At different sampling dates throughout the season, these natural enemy taxa responded in varying ways to the availability of alternative prey and resources available within prairie land cover. Within this system, prairie integration had a significant impact on the abundance and diversity of arthropods; however the surrounding matrix of each site was dominated by prairie, and likely silenced the treatment effects.</p
Sampling and management of aphidophagous natural enemies in Iowa soybean
No full textIn Iowa, surveys of natural enemies in soybean [Glycine max (L.) Merr.] conducted before the arrival of Aphis glycines Matsumara (Hemiptera: Aphididae) revealed several species that may contribute to the mortality of A. glycines. In 2004 and 2005, several sampling methods were investigated to determine if diversity of the natural enemy community in Iowa soybean has changed with the arrival of A. glycines. We hypothesized that the natural enemy community in soybean has changed with the introduction of A. glycines and that sampling methods would collect different species of natural enemies. Also, with the use of an alfalfa living mulch, we investigated the impact of natural enemies on A. glycines. We hypothesized that a living mulch would increase the abundance of the aphidophagous community in soybean and suppress A. glycines establishment and population growth.</p
Developing a decision‐making framework for insect pest management: a case study using Aphis glycines (Hemiptera: Aphididae)
No full textBACKGROUND: The profitability of farming varies based on factors such as a crop's market value, input costs and occurrence of resistant pests, all capable of altering the value of pest management tactics in an integrated pest management program. We
provide a framework for calculating expected yield and expected net revenue of pest management scenarios, using the soybean aphid (Aphis glycines) as a case study. Foliar insecticide and host-plant resistance are effective management tactics for preventing
yield loss from soybean aphid outbreaks; however, pyrethroid-resistant aphid populations pose a management challenge for farmers. We evaluated eight scenarios relevant to soybean aphid management in Iowa with varying probabilities of aphid outbreaks and insecticide-resistant aphids occurring.
RESULTS: Our equation suggests that insecticide use is profitable when the probability of an aphid outbreak is ≥29%, and soybean production will become more costly with increasing probability of pyrethroid-resistant aphids. If farmers continue to use pyrethroids, they will not experience financial consequences from pyrethroid-resistant aphids until the chance of insecticide resistance is 48%. Aphid-resistant varieties provided consistent yield and offered the highest net revenue under all conditions.
CONCLUSION: This framework can be used for other crop–pest systems to evaluate the profitability of management tactics and investigate howresistance impacts revenue for farmers. Including the cost of resistance in crop budgets can help farmers and agronomic
consultants comprehend these impacts and enhance decision-making to increase revenue and curb resistance development.This article is published as Dean, Ashley N., Jarad B. Niemi, John C. Tyndall, Erin W. Hodgson, and Matthew E. O'Neal. "Developing a decision‐making framework for insect pest management: a case study using Aphis glycines (H emiptera: A phididae)."Pest Management Science 77 (2021):886-894, which has been published in final form at doi: 10.1002/ps.6093.</p
Soybean aphid (Hemiptera: Aphididae) response to lambda‐cyhalothrin varies with its virulence status to aphid‐resistant soybean
No full textBACKGROUND: Soybean aphid, Aphis glycines, is an invasive insect in North America, considered one of the most important pests of soybean. Their management relies heavily on foliar insecticides, but there is growing effort to expand these tools to include aphid-resistant varieties. We explored if the LC50 and LC25 of lambda-cyhalothrin varied between virulent (Resistance to Aphis glycines (Rag) soybeans) and avirulent (susceptible to Rag-genes soybeans) populations of soybean aphid with a leaf-dip bioassay. We also investigated the response to the LC25 of lambda-cyhalothrin on adults (F0) and their progeny (F1) for both avirulent and virulent soybean aphid.
RESULTS: The LC50 of the virulent aphid population was significantly higher compared with the LC50 of the avirulent population. The LC25 significantly reduced fecundity of the F0 generation of avirulent soybean aphid, but no significant effect was observed for virulent aphids. In addition, the LC25 significantly shortened the adult pre-oviposition period (APOP) and lengthened total pre-oviposition period (TPOP) of avirulent aphids, while the mean generation time (T) was significantly increased. For the virulent aphid, sublethal exposure significantly lengthened development time of first and third instars, TPOP, and adult longevity. In addition, all demographic parameters of virulent soybean aphid were significantly affected when they were exposed to the LC25 of lambda-cyhalothrin.
CONCLUSION: Our results demonstrate lambda-cyhalothrin is less toxic to virulent aphids and exposure to the LC25 can trigger hormesis which may have implications for the long-term management of this pest with this insecticide as well as with aphid-resistant varieties of soybean.This is the peer reviewed version of the following article: Valmorbida, Ivair, Dionei S. Muraro, Erin W. Hodgson, and Matthew E. O'Neal. "Soybean aphid (Hemiptera: Aphididae) response to lambda‐cyhalothrin varies with its virulence status to aphid‐resistant soybean." Pest management science (2019), which has been published in final form at doi: 10.1002/ps.5661. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.</p
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