Final report for LNE22-455R
Project Information
a. Problem, Novel Approach, and Justification
b. Objectives, Questions, and Research Plan
Our overarching goal was to develop an innovative push-pull system for managing SWD that reduces reliance on insecticides across conventional, organic, and U-pick small fruit operations. By minimizing pesticide use, this system aims to lower environmental risks while enhancing the sustainability and profitability of the small fruit industry—an industry currently threatened by this invasive pest in the Northeastern U.S.
We addressed the following questions in laboratory and field experiments:
(1) Test the repellency efficacy of novel natural and biorational products. Do compounds from fungal pathogens and fermented apple juice act as repellents, oviposition deterrents, and/or toxins for SWD? Do new biorational compounds repel SWD?
(2) Demonstrate the efficacy of activators of crop defenses on SWD. Do commercially available activators of crop defenses reduce preference and performance of SWD in fruits?
(3) Develop a novel push-pull strategy. Does the combination of attractants and repellents reduce SWD infestation?
c. Outreach plan
We disseminated information through presentations at regional grower meetings, newsletter articles, field demonstrations, and factsheets. We conducted two webinars: one on SWD biology, ecology, and management and another on behavior-based strategies to manage SWD. Information was posted at the StopSWD.org website http://www.stopswd.org/index.cfm, hosted by the NE IPM Center. We created two short 4-min videos and conducted two surveys (at the beginning and at the end of the project) to measure changes in farmer knowledge and their willingness to adopt our proposed approaches.
To reduce farmer reliance on insecticides in Northeastern USA small fruit crops, we will develop and provide recommendations on a new, environmentally friendly push-pull strategy to manage SWD. Here, we will: (1) test the efficacy of novel natural repellents/oviposition deterrents/toxins for SWD, (2) demonstrate the efficacy of commercially available activators of crop defenses to reduce SWD fruit infestation, and (3) develop a novel and effective push-pull strategy that will combine repellents/oviposition deterrents/toxins with an existing attractant-and-kill approach. Our proposed Extension plan will allow novel and sustainable behavior-based approaches to be adopted by conventional, organic, and U-pick farmers in the Northeast.
Following the arrival of spotted-wing drosophila (SWD), Drosophila suzukii, in the United States, small fruit IPM programs were significantly disrupted and largely replaced by insecticide-driven approaches. To offer alternative management options, the development of behavior-based strategies has become essential. In response, we identified and tested novel plant-derived compounds with repellent properties that can be applied directly as repellents or integrated into a push-pull strategy.
Cooperators
- (Researcher)
- (Researcher)
Research
Our goal is to identify novel natural compounds that act as repellents/oviposition deterrents/toxins for SWD and use them in combination with a commercial attract-and-kill formulation to develop an innovative push-pull system for SWD. We hypothesize that adding a repellent/oviposition deterrent/toxic compound in the crop will increase the efficacy of attract-and-kill approaches.
Our specific questions are (1) do compounds from fungal pathogens and fermented apple juice act as repellents/oviposition deterrents/toxins for SWD? (2) Do commercially available activators of crop defenses reduce preference and performance of SWD in fruits? (3) Does the combination of repellents with attractive lethal baits reduce SWD infestation?
- Repellency of natural and biorational products
1.a) Fungal pathogens
Fourteen volatile organic compounds were identified from anthracnose-infected blueberries and screened for their potential repellent effects on SWD in laboratory choice assays. Initial multiple-choice assays evaluated SWD adult responses to blueberries treated with these compounds after a 24-hour exposure.
From the original fourteen, nine compounds were selected for further testing. These were evaluated in dual-choice (2-choice) assays using gated-trap vials to compare SWD preference between treated and untreated blueberries, again after a 24-hour period.
Based on results from both the multiple-choice and 2-choice assays, two compounds—ethyl butyrate and ethyl crotonate—were chosen for further study. Dose-response behavioral assays were conducted in 2-choice arenas under laboratory conditions, comparing fly attraction and oviposition on treated versus untreated blueberries. After 2 hours, the number of flies captured in each gated-trap vial and the number of eggs laid in the fruits were recorded. To assess olfactory sensitivity, electroantennogram (EAG) assays were conducted to measure SWD antennal responses to both compounds across a concentration gradient, with volatiles diluted in hexane and compared against a hexane control.
In summer 2023, field cage studies were conducted using potted blueberry plants to test the repellency of ethyl butyrate and ethyl crotonate delivered via sachets. Tomato cages were placed over each plant, and five clusters of approximately ten berries were suspended randomly within each cage. Fifty SWD adults (1:1 male:female) were released per cage, and after 24 hours, berries were collected to assess oviposition. These berries were later incubated to determine adult emergence.
In summer 2024, additional field cage studies were conducted to compare the repellency of ethyl butyrate and ethyl crotonate to the known repellent 2-pentylfuran. Large mesh cages (5.5 m in length) enclosed five mature blueberry plants. Sachets were placed on a designated “focal bush” at one end of each cage, and 30 SWD adults (1:1 M:F) were released between each of the five plants (N=120 per cage) to ensure even fly distribution. At 1, 2, and 3 days post-treatment, fifty berries were sampled from the canopy and base of the focal, center, and end bushes. Eggs were counted within 24 hours of collection, and berries were incubated to assess adult emergence.
1.b) Methyl benzoate and analogs
Laboratory choice assays were conducted to evaluate the repellency and ovipositional deterrent effects of methyl benzoate and nine of its chemical analogs against SWD, using Geosmin as a known repellent control. Assays involved blueberries treated with test compounds, and adult SWD were introduced to assess both attraction and oviposition behavior. Treated berries were incubated for 14 days, after which adult emergence was recorded.
To further evaluate methyl benzoate under semi-field conditions, cage studies were conducted in a commercial blueberry field at the P.E. Marucci Center for Blueberry and Cranberry Research (Chatsworth, NJ). Each cage enclosed a single blueberry bush, and treated and untreated blueberries were placed on opposite sides within the cage. Adult SWD were introduced, and after 24 hours, berries were examined for eggs. These berries were then incubated for 14 days to quantify adult emergence.
- Efficacy of plant defense activators
Three crop bioactivators (Actigard, Lifegard, and Regalia) and one crop sterilant (Oxidate) were tested for their potential to induce fruit-mediated repellency or deterrence against SWD. These products were applied directly to blueberry fruits in both semi-field and large field cage trials to evaluate whether elicitor or sterilant treatments could alter fruit characteristics in a way that reduces SWD attraction or oviposition.
In the semi-field trials, clusters of ‘Bluecrop’ blueberries were enclosed in fine mesh bags before ripening to prevent prior infestation. Once ripened, berries were sprayed inside the bags with each treatment. Treated fruit were then collected at 1, 3, 7, and 10 days post-treatment and used in laboratory assays to assess SWD oviposition in both choice and no-choice setups, as well as to evaluate adult attraction over time.
In the large cage field trials, four replicates of each treatment plus a blank control were tested using five mature ‘Duke’ blueberry bushes per cage. Fruits on each bush were sprayed to runoff with the assigned treatment. After 24 hours, 100 adult SWD (1:1 male:female) were released into each cage. Berries were harvested at 3, 7, and 10 days post-treatment and incubated for two weeks to quantify SWD adult emergence as a measure of treatment efficacy.
- Development of a push-pull strategy
An on-farm field study was conducted to evaluate a push-pull system, using methyl benzoate as the push component and yellow vane traps baited with an attractant and a soapy-water drowning solution as the pull. In control plots (no-pull), yellow vane traps without attractant were used to rule out trap presence as a confounding attractant. The study was implemented as a randomized complete block design over four weeks. Weekly, berries were collected from each plot, and traps were inspected for SWD presence. Collected berries were checked for eggs and incubated to assess adult emergence.
- Repellency of natural and biorational products
1.a) Fungal pathogens
Fourteen volatile compounds were identified from anthracnose-infected blueberries, and initial experiments revealed that nine of these compounds exhibited repellent properties. Dose-response studies were conducted for two of these compounds, ethyl butyrate and ethyl crotonate, which were tested in field cages during the 2023 season.
In 2-choice assays, two compounds—ethyl butyrate and ethyl crotonate—showed greater than 90% repellency, and thus were selected for further laboratory and cage studies. Dose-response experiments demonstrated that both compounds exhibited a dose-dependent repellent effect on SWD. However, when a 1:1 mixture of the two compounds was tested, no dose-dependent effect was observed. Each compound individually produced a strong, dose-dependent response, comparable to the known SWD repellent 2-pentylfuran.
In field cage trials with potted plants, the two novel repellents, along with 2-pentylfuran, were tested for their effect on oviposition. Both ethyl butyrate and ethyl crotonate reduced the number of eggs laid per berry to a similar extent. The combination of the two compounds in a 1:1 blend also reduced oviposition, but the effect was not significantly different from either compound applied individually. A repellency index (Control-Volatile/Total) confirmed that individual compounds and the blend showed similar repellent effects. Field testing in full-scale cages covering blueberry bushes in the field resulted in a significant reduction in both egg-laying per berry and adult emergence, with ethyl crotonate performing the best among all repellents tested.
Results from these studies were published in two peer-reviewed articles:
Caitlin, R., Quadrel, A., Urbaneja-Bernat, P., Beck, J.J., Ben-Zvi, Y., Khodadadi, F., Aćimović, S.G., and Rodriguez-Saona, C. 2023. Blueberries infected with the fungal pathogen Colletotrichum fioriniae release odors that repel Drosophila suzukii. Pest Management Science 79(12): 4906-4920. doi: 10.1002/ps.7692.
Quadrel, A., Ferguson, B., Rering, C.C., Urbaneja-Bernat, P., and Rodriguez-Saona, C. 2025. Two volatiles from anthracnose-infected blueberries trigger electrophysiological and aversive behavioral responses in Drosophila suzukii. Journal of Economic Entomology. Special Collection on “De-coding the Role of Insect Communication in Sustainable Agriculture”. doi: 10.1093/jee/toaf032
1.b) Methyl benzoate and analogs
Among the compounds tested, one analog of methyl benzoate performed similarly to Geosmin, while another exhibited some repellent properties. To further evaluate the efficacy of these compounds, additional behavioral and toxicity assays were conducted both in the laboratory and in the field during the 2023 season.
- Efficacy of plant defense activators
The effectiveness of plant defense activators was inconclusive based on results from both semi-field and field cage experiments. Given these findings, no further testing of these elicitors will be conducted at this time.
Results from these studies were published in a peer-reviewed journal:
Quadrel, A., Urbaneja-Bernat, P., Holdcraft, R., and Rodriguez-Saona, C. 2024. Elicitors of plant defenses as a standalone tactic failed to provide sufficient protection to fruits against spotted-wing drosophila. Frontiers in Agronomy 6:1381342, section Pest Management. Research Topic on “Latest Research Advances in Biology, Ecology, and Integrated Pest Management of Invasive Insects”. doi: 10.3389/fagro.2024.1381342.
- Development of a push-pull strategy
Methyl benzoate was tested in combination with baited traps as part of a push-pull system to assess its potential for SWD management in blueberry fields. In the field trials, berries from ‘push’-only and ‘push-pull’ plots showed a reduced proportion of berries infested with SWD eggs compared to untreated control plots. Additionally, these plots had fewer eggs per berry. However, only the baited yellow-vane traps effectively captured SWD adults. ‘Pull’-only plots, in contrast, did not show significant reductions in either the proportion of berries with eggs or the number of eggs per berry, suggesting that the ‘pull’ component is not effective when used alone.
Results from these studies were published in a peer-reviewed journal:
Gale, C.C., Ferguson, B., Rodriguez-Saona, C., Shields, V.D.C., and Zhang, A. 2024. Evaluation of a push–pull strategy for spotted-wing drosophila management in highbush blueberry. Insects 15, 47. doi: 10.3390/insects15010047
The novel natural products tested have shown promising potential for improving control of spotted-wing drosophila (SWD) under laboratory, semi-field, and on-farm conditions. Both the floral volatile methyl benzoate and the compounds associated with fungal infection, ethyl crotonate and ethyl butyrate, significantly reduced oviposition and adult emergence compared to control treatments or known repellents. However, further refinement of deployment methods is necessary before these volatiles can be effectively incorporated into existing Integrated Pest Management (IPM) programs.
Education & Outreach Activities and Participation Summary
Educational activities:
Participation Summary:
Presentations at Scientific Meetings
The results from this study were presented at eight national and international scientific conferences:
Quadrel, A. and Rodriguez-Saona, C. 2022. Identifying repellents for spotted-wing drosophila from anthracnose-infected fruits. Joint Annual Meeting of the Entomological Society of America (ESA), Entomological Society of Canada (ESC), and the Entomological Society of British Columbia (ESBC). Vancouver, BC, Canada. (WINNER: 2nd place student oral competition).
Ferguson, B.E., Rodriguez-Saona, C., Zhang, A., and Urbaneja-Bernat, P. 2022. Ovipositional deterrent/repellent capabilities of naturally existing methyl benzoate and its analogs to manage Drosophila suzukii. Joint Annual Meeting of the Entomological Society of America (ESA), Entomological Society of Canada (ESC), and the Entomological Society of British Columbia (ESBC). Vancouver, BC, Canada.
Quadrel, A., Rodriguez-Saona, C., and Rering, C. 2023. Dose-dependent behavioral response of spotted-wing drosophila to anthracnose volatiles. Eastern Branch Meeting of the Entomological Society of America (ESA). Providence, Rhode Island. (WINNER: 1st place Masters student oral competition)
Rodriguez-Saona, C., Quadrel, A., Rering, C., and Urbaneja-Bernat, P. 2023. Behavioral response of the invasive spotted-wing Drosophila to anthracnose-infected fruit volatiles. Symposium on “Semiochemicals and their application in pest management”. 38th Annual Meeting of the International Society of Chemical Ecology. Bengaluru, India.
Quadrel, A., Rodriguez-Saona, C., and Rering, C. 2023. Field efficacy of anthracnose-infected blueberry volatiles as repellents for spotted-wing drosophila. Annual Meeting of the Entomological Society of America (ESA). National Harbor, Maryland. (WINNER: 1st place student oral competition)
Rodriguez-Saona, C., Quadrel, A., Urbaneja-Bernat, P., and Polashock, J. 2024. Can elicitors of defenses enhance resistance in berry crops against insect pests? 39th Annual Meeting of the International Society of Chemical Ecology. Prague, Czech Republic.
Rodriguez-Saona, C., Quadrel, A., Rering, C., and Urbaneja-Bernat, P. 2024. Decoding the semiochemically-mediated interactions among an invasive insect pest, a pathogen, and their fruit host. XXVII International Congress of Entomology, Kyoto, Japan.
Ferguson, B., C. Gale, A. Zhang, and C. Rodriguez-Saona. 2024. Big push-little pull: Repellent effects of methyl benzoate drive reduced spotted-wing infestation in blueberries. Annual Meeting of the Entomological Society of America (ESA). Phoenix, Arizona (Invited Talk in Symposium: Multifunctional Chemicals? Plant Volatiles Influence Herbivores, Pollinators, and Natural Enemies)
Presentations at Grower Meetings
Rodriguez-Saona, C. 2025. Rebuilding IPM: Advances in SWD Management. Scotia Horticultural Congress/Nova Scotia, Canada. Attendance = 52.
Rodriguez-Saona, C. 2024. Novel behavior-based strategies for SWD. New England Vegetable and Fruit Conference/Manchester, New Hampshire. Attendance = 60.
Rodriguez-Saona, C. 2024. SWD management: Adjuvants, biocontrols, repellents, and insecticides. Mid-Atlantic Fruit and Vegetable Convention/Hershey, Pennsylvania. Attendance = 105.
Proceedings
Rodriguez-Saona, C. and Ferguson, B. 2025. Update on spotted-wing Drosophila research and management. Proceedings of the Atlantic Coast Agricultural Convention and Trade Show. Atlantic City, New Jersey.
Rodriguez-Saona, C. 2024. Novel behavior-based strategies for SWD. Proceedings of the New England Vegetable and Fruit Conference. Manchester, New Hampshire.
Rodriguez-Saona, C., Holdcraft, R., Ferguson, B., and Axtell, A. 2024. SWD management: Adjuvants, biocontrols, repellents, and insecticides. Proceedings of the Atlantic Coast Agricultural Convention and Trade Show. Atlantic City, New Jersey.
Webinars
2023: Cesar Rodriguez-Saona (PI). Webinar panelist: July What's Bugging You First Friday on SWD and spiders. Provided an overview of spotted-wing drosophila biology and management.
2022: Cesar Rodriguez-Saona (PI). Webinar panelist: Advances in behavior-based tactics for management of spotted-wing drosophila. Provided an overview of spotted-wing drosophila bevavior-based control strategies.
Videos
Salt Flotation Method to Monitor Spotted-Wing Drosophila Larvae https://www.youtube.com/watch?v=eZwqnLN-Tg4
Methods to Study Spotted-Wing Drosophila Behavior (In Progress)
Learning Outcomes
Survey Summary:
In Year 1 (2023), we received 10 survey responses, with 3 (30%) fully completed and 7 (70%) partially completed. In contrast, Year 2 (2024) saw an increase in both participation and completion, with 24 total responses—17 (71%) fully completed and 7 (29%) partial.
SWD was reported at 70% of farms in 2023 and 54% in 2024. Among those reporting SWD, 70% experienced damage in 2023 compared to just 13% in 2024. The primary management method for SWD was the application of conventional insecticides, used by 90% of respondents in 2023 and 75% in 2024. Most growers reported applying 5–6 sprays per season. The most commonly used insecticides, in descending order, were pyrethroids, carbamates & organophosphates, and neonicotinoids.
SWD monitoring was conducted by 40% of growers in 2023 and 33% in 2024. Most of these growers utilized either vinegar-based traps or Rutgers' IPM scouting program. Among those who scouted, fruit damage assessments were also used to detect SWD—reported by 20% in 2023 and 50% in 2024.
Interest in integrated pest management (IPM)-based strategies increased significantly, with 67% of growers in 2024 expressing interest, up from 30% in 2023. Trap-based thresholds consistently emerged as a strategy growers would be willing to adopt. There was also notable interest in repellents and oviposition deterrents, other behavior-based tactics, biological control, and the use of border sprays. In contrast, there was little to no interest in sanitation improvements or protective netting.
Overall, grower interest in non-chemical SWD management strategies increased from 2023 to 2024, along with greater survey participation. In particular, there was a rise in reported scouting activity and interest in behavioral control techniques.
Project Outcomes
Four peer-reviewed articles were published from this project:
Caitlin, R., Quadrel, A., Urbaneja-Bernat, P., Beck, J.J., Ben-Zvi, Y., Khodadadi, F., Aćimović, S.G., and Rodriguez-Saona, C. 2023. Blueberries infected with the fungal pathogen Colletotrichum fioriniae release odors that repel Drosophila suzukii. Pest Management Science 79(12): 4906-4920. doi: 10.1002/ps.7692.
Quadrel, A., Ferguson, B., Rering, C.C., Urbaneja-Bernat, P., and Rodriguez-Saona, C. 2025. Two volatiles from anthracnose-infected blueberries trigger electrophysiological and aversive behavioral responses in Drosophila suzukii. Journal of Economic Entomology. Special Collection on “De-coding the Role of Insect Communication in Sustainable Agriculture”. doi: 10.1093/jee/toaf032
Quadrel, A., Urbaneja-Bernat, P., Holdcraft, R., and Rodriguez-Saona, C. 2024. Elicitors of plant defenses as a standalone tactic failed to provide sufficient protection to fruits against spotted-wing drosophila. Frontiers in Agronomy 6:1381342, section Pest Management. Research Topic on “Latest Research Advances in Biology, Ecology, and Integrated Pest Management of Invasive Insects”. doi: 10.3389/fagro.2024.1381342.
Gale, C.C., Ferguson, B., Rodriguez-Saona, C., Shields, V.D.C., and Zhang, A. 2024. Evaluation of a push–pull strategy for spotted-wing drosophila management in highbush blueberry. Insects 15, 47. doi: 10.3390/insects15010047
A patent has been submitted as a result of this project.
Our findings on SWD repellents are based on laboratory, semi-field, and caged field trials; therefore, definitive recommendations for on-farm implementation cannot yet be made. Additional field testing is required to determine optimal deployment strategies and application rates for the most promising repellents. Nevertheless, this work represents significant progress toward the identification and preliminary validation of novel repellent and oviposition-deterrent compounds for SWD. These results lay a strong foundation for future research aimed at developing sustainable, behavior-based management tools for this invasive pest.
Information Products
- Evaluation of a Push–Pull Strategy for Spotted-Wing Drosophila Management in Highbush Blueberry
- Blueberries infected with the fungal pathogen Colletotrichum fioriniae release odors that repel Drosophila suzukii
- Two volatiles from anthracnose-infected blueberries trigger electrophysiological and aversive behavioral responses in Drosophila suzukii (Diptera: Drosophilidae)
- Elicitors of plant defenses as a standalone tactic failed to provide sufficient protection to fruits against spotted-wing drosophila
- Salt Flotation Method to Monitor Spotted-Winged Drosophila Larvae