Performing Department
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Non Technical Summary
A major challenge in US agriculture is the sustainable management of insect pests that threaten food security. One line ofdefense is the use of insect predators and parasitoids (natural enemies) as biological control agents in integrated pestmanagement programs. Natural enemies provide benefits to crops by directly consuming pests and thus reducing crop damage.However, it has also been shown that the mere presence of their natural enemies can modify pest physiology and behaviorthat might reduce their impacts on crops. One way to mimic the presence of a predator is to simulate the cues that pest insectsuse to determine that danger is nearby, such as the visual, vibratory, or odor cues. This work proposes to understand the role ofnatural enemy odor cues in eliciting changes in pest insect behavior and damage to agricultural crops. Preliminary data suggestthat lady beetle odor cues influence the movement and reproductive capacity of a notorious crop pest - aphids. While thisresearch has shown that aphids are impacted by predator odor cues, few studies have directly confirmed that aphids can detectnatural enemy odor cues, and whether aphids will respond to these cues in natural settings. This proposal will expand this workby 1) determining whether cues from two different natural enemies (lady beetles and parasitic wasps) interact to enhance risk effects or whether other natural enemies are deterred by the presence of lady beetle odor cues, and 2) examining the impact of natural enemy odor cues on aphid abundance and other pest and beneficial insects in a fieldsetting. Overall, this work will advance the Priority Area of Plant Health and Production by reducing agrichemical inputs and increasing the efficiency of sustainable pest management strategies.
Animal Health Component
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Research Effort Categories
Basic
100%
Applied
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Developmental
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Goals / Objectives
A major challenge in US agriculture is the sustainable management of insect pests that threaten food security. One line ofdefense is the use of insect predators and parasitoids (natural enemies) as biological control agents in integrated pestmanagement programs. Natural enemies provide benefits to crops by directly consuming pests and thus reducing crop damage.However, it has also been shown that the presence of predators or their cues can elicit non-consumptive effects in preyphysiology and behavior that might reduce pest impacts on crops. In order to maximize the impact that natural enemies have onpests, we must also harness non-consumptive effects in pest management strategies. The use of natural enemy chemical cuesto enhance crop protection represents a new frontier in applied agricultural entomology. The overall goal of this postdoctoral fellowship was to situate the PD to be competitive for a research-teaching faculty position.This project was transferred from the PD's postdoctoral instiution to a new institution where the PD is now an Assistant Professor. The objectives of the original project are as follows, indicating both previous progress made and future progress intended at the current institution.Career/Training Objectives: Progress and Future Objectives:Objective 1: Develop an independent research program on insect ecology in agroecosystemsDuring the award period, I interviewed and was hired for an Assistant Professor position at Montana State University to initiate a research program on insect ecology in agroecosystems. I was also elected by my peers to serve as the co-chair for the Gordon Research Seminar on Plant-Herbivore Interactions, where I will be charged with developing the scientific program for the conference held in February 2025.Objective 2: Expand upon mentorship skills by engaging with undergraduate and graduate students in teaching and researchI successfully created and taught a 1-credit graduate course on Insect Ecology at Penn State University which received positive evaluations. This course was pitched to Montana State University during my interview, and now I am developing a 3-credit Insect Ecology course. My experience developing the Insect Ecology seminar at PSU was a key asset to my CV during my interview at Montana State, in which they needed a candidate with a strong teaching background to reinvigorate a core undergraduate survey course on Insects and Human Society. Undergraduate research was heavily supported on this grant, including 7 undergraduate research assistants, with 5 of them completing independent research projects and poster presentations. One undergraduate co-authored manuscript has been published, with two more in prep. One of these undergraduate researchers is now moving to Montana State as a graduate student in my lab.Objective 3: Strengthen my proficiency in scientific communication with the public.This award supported PD participation in 3 community outreach events. This award also supported the PD co-authoring a popular press article with a graduate student for the American Entomologist focused on making lab spaces welcoming to students. This award supported 7 PD invited conference presentations, including the Project Directors Meeting held in conjunction with the Entomological Society of America Meeting.Plans for Transferred FundingObjective 1: This funding would allow me to fulfil a goal of organizing a symposium focused on pest insect ecology at a scientific conference and integrate the students who will be supported on this award into the planning process as a professional development opportunity for them.Objective 2: This funding will support a graduate and recruitedundergraduate researchers from diverse backgrounds and underrepresented groups in the sciences. Students will be encouraged to participate in teaching training and guest lecture opportunities to gain experience with science communication and instruction. Additionally, the funding transfer will support the publication of 2 peer-reviewed journal articles co-authored by undergraduate researchers from Penn State University and authorship opportunities for student researchers at Montana State for 2 new publications.Objective 3: This funding will allow initiation of science communication opportunities for graduate and undergraduate students through outreach events at Montana State University.Research Project Plan: Progress on ObjectivesObjective 1. Do aphids detect and respond to isolated natural enemy odor cues?Work on this objective also allowed us to file for a patent for using the odors of lady beetles to control pest insects. Experiments were conducted specifically to continue to address this question in collaboration with the behavioral ecology lab at PSU. The methodology for using the electroantennogram with this organism has been challenging to execute, but strides have been made to confirm bioactivity for the lady beetle odors. New collaborators have been established to better support this aspect of the project. It appears that the wasp adults do not initiate odor-derived changes in aphid behavior, but aphid exposure to parasitized conspecifics or wasp pupae does elicit avoidance responses and reduction in aphid nymph production. This discovery opened a great area of exploration of parasitoid non-consumptive effects that has resulted in an in-prep publication and garnered great interest at two invited presentations in 2023 with anticipated future research on this topic.Objective 2. Does exposure to natural enemy odor cues affect aphid populations?A research article assessing whether aphid populations are affected by lady beetle odor cues was published in Basic and Applied Ecology in 2023. An additional publication on the impacts of lady beetle footprint trails on aphid performance and behavior is in prep. Work was completed addressing aphid population response to parasitic wasp risk cues in isolation, resulting in an in-prep publication. All experiments found that predation risk, either via chemical cues or other cues, resulted in reduced pest aphid populations.Objective 3. Does exposure to natural enemy odor cues affect aphid populations and the composition of insect communities in the field?A field trial for Objective 3 was completed in the Summer of 2022, but the results were inconclusive due to extreme herbivory from grasshoppers and intense weeds. The results do suggest that the lady beetle odor cues may also impact pest species beyond aphids. In 2023, Objective 3 could not be trialed again due to the job change of the PI of the grant but is intended to be completed if the funding is extended.Plans for Transferred Funding: Complete Objectives 2 & 3:Continued funding on this project will allow us to bring together the knowledge previously gained of isolated effects of natural enemies on aphid populations to provide a crucial missing piece of information on whether combined natural enemy cues have additive effects on aphid performance.During the award period, we were unable to execute the proposed experiment in Objective 2 combining the effects of both parasitic wasps and lady beetles on aphid populations. Several related research questions which would enrich our understanding of the objectives include whether parasitic wasps avoid plants containing lady beetle odor cues, and thus reduce biological control potential by parasitic wasps. This work has great potential as another stand-alone publication resulting from this award. Additionally, extending the award would allow us to retrial the field experiment to investigate whether these consequences for pest populations are maintained in less controlled environments. This experiment will allow another opportunity for a publication and to assess the suitability of this novel pest management strategy for field application.
Project Methods
Objective 2: Does exposure to natural enemy odor cues affect aphid populations?Rationale: Lady beetle odors reduce aphid fecundity and population size, but this affect can vary by timing and duration of exposure(Hermann et al. 2021, Kansman 2023). However, the odors of adult parasitic wasps do not appear to affect aphid performance (Kansman, in prep). It is still unknown whether the presence of lady beetle chemical cues will reduce or enhance the efficacy of parasitic wasps as biological control agents.Methods: A group of 20 adult aphids will be added to a single 4-week old collard plant within a 60 × 60 × 60 cm mesh-nyloncage on a greenhouse bench. After allowing the aphids to settle for 24 hours, each cage will receive either a free-moving (lethal)or caged (risk) natural enemies. The natural enemy treatments include: lethal lady beetle (1 male + 1 female), lethal parasitoid(2 female), combined lethal (1 lady beetle (male) + 1 female parasitoid), lady beetle risk (2 caged), lady beetle risk (2 caged) and parasitoid lethal (2 female),and a natural enemy-free control. The natural enemies in the risk treatments will be caged within opaque mesh metal cages (tea infusers) to inhibit visual and tactile cues but allow for chemical cues and will be tied to the top of the plant cage. Moistened cotton will be provided in each tea infuser to provide sustenance for the natural enemies. The treatments will be replicated 5 times for a total of 35 cages. Aphids will be exposed to the natural enemy treatments for 24 hours before the treatments are removed. Aphid abundance will be assessed every 3 days until parasitoid mummies can be quantified (4 sample times).The response of aphid abundance to the natural enemy cue treatments will be assessed over time and compared across treatments using repeated-measuresANOVA. We will use a t-test to compare the number of winged aphids in the natural enemy treatments to the natural enemy-freecontrols. We will also compare theparasitoid mummies present in the lady beetle treatments compared to the lady-beetle free treatments.Expected Outcomes: Lethal natural enemy treatments will reduce aphid abundance, with the largest reduction inaphid abundance in the combined natural enemy treatment. If consistent with prior work in the lab, aphid exposure to predationrisk will result in increased nymph production. The combined natural enemy treatment will elicit a stronger response than eithernatural enemy independently. Parastoid mummy abundance will be affected by the presence of lethal lady beetles and risk lady beetles, with the highest predicted parasitism rates in the lady beetle risk treatment and the beetle-free treatment.In addition, I predict that aphid wing production will increase in the presence of natural enemies in both lethal and risk treatments.Objective 3: Does exposure to natural enemy odor cues affect aphid populations and the composition of insectcommunities in the field?Rationale: In order to know whether we can harness non-consumptive effects as a pest management tool, we need tounderstand whether aphids respond to odor cues in the field. In addition, it is essential to understand how manipulation of thenon-consumptive interactions between organisms affects the other members of the insect community, especially beneficialinsects. Given our previous results that the odors of parasitic wasps do not stimulate predation risk responses in aphids, we will exchange the parasitoid odor treatment for released parasitoids within the closed field cages, and pay special attention to lady beetle and parasitoidpresence within the open field plots.Methods: This study will be conducted within closed and open mesh field cages.Each 1.2 × 1.2 m cage will contain one 6-week old potted collard plant that will receive 50 adult aphids. The cage will receive one of 4 natural enemy treatments: Lady beetle (2 male + 2 female) risk Treatments , parasitoid (4 female) lethal treatments, combined (2 lady beetles risk treatments+ 2 parasitoid lethal treatments), and a no-natural enemy control. The risk treatments will be administered in metal tea infusers attached to the top of the cage, with moistened cotton provided (insects replaced as necessary). The cages will either be closed to prevent external insect colonization, or open on two sides to allow the natural colonization of the broader arthropod community. The predator treatment and cage condition will be replicated 5 times or a total of 64 cages. Aphid density and the composition of the insect community will be assessed weekly through visual surveys and passive sticky cards. Surveys will take place for 6 weeks. We will model the effect of the natural enemy risk treatment on aphid abundance, pest insect abundance, and natural enemy abundance over time using generalized linear models.Expected Outcomes: In the closed cages, aphid abundance will increase in response to the natural enemy risk treatment due to their inability to disperse and switch in reproductive strategy noted in Hermann 2021. The greatest aphid suppression will occur in the cage with the combined predation risk treatment and lethal parasitoid treatment.In the open cages, I predict aphid wing production will increase in response to the risk cues, resulting in lower aphid abundance as aphids emigrate from the open plots. Diverse natural enemy assemblages will elicit stronger impacts on aphid abundance than single natural enemy treatments.