Progress report for LNE22-455R
Project Information
a. Problem, Novel Approach, and Justification
The invasion of spotted-wing drosophila (SWD), Drosophila suzukii (Matsumura), into the Northeast USA in 2011 has severely disrupted small fruit Integrated Pest Management (IPM) programs. Native to Southeast Asia, SWD has become the most important insect pest of small fruits throughout the USA. SWD attacks a wide variety of fruit crops, including blueberries, blackberries, raspberries, strawberries, and cherries, with a combined annual value of over $5.8 billion in the USA, and causes losses that exceed $718 million annually. Currently, growers rely on a single management strategy—aggressive, calendar-based conventional insecticide applications. We propose a more sustainable alternative method for SWD control based on behavior manipulation called push-pull, which combines the use of an attractant (the pull component) with a repellent/deterrent compound (the push component). Adoption of an effective push-pull system by conventional, organic, and U-pick growers, should drastically reduce the frequency of conventional insecticide applications and thus reduce operating costs, suppress the development of insecticide-resistant populations, and minimize negative impacts on biological control agents. Our project addresses the #1 research priority for small fruits for the Northeastern IPM Center, which is “new and emerging pests.” Based on stakeholder feedback, future research should focus on the development of behavior-based strategies, such as push-pull, which is the goal of this proposal.
b. Objectives, Questions, and Research Plan
Our overarching goal is to develop an innovative push-pull system for SWD that will reduce reliance on insecticide use in conventional, organic, and U-pick small fruit operations. Our system will reduce environmental risks and increase sustainability and profitability of the small fruit industry currently jeopardized by this invasive species in the Northeast.
We will address 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 will disseminate information through presentations at regional grower meetings, newsletter articles, field demonstrations, and factsheets. We will conduct two webinars: one on SWD biology, ecology, and management and another on behavior-based strategies to manage SWD. Information will be posted at the StopSWD.org website http://www.stopswd.org/index.cfm, hosted by the NE IPM Center. We will create two short 4-min videos and conduct 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.
Research
Fungal Pathogens
Fourteen volatile organic compounds were identified from anthracnose-infected blueberries. These compounds were tested for repellency effects on spotted-wing drosophila (SWD) in choice experiments in laboratory assays. Assays examined SWD adult response to blueberries treated with the compounds in multiple-choice assays after 24 hours.
From the original fourteen compounds, nine were selected for further testing. Dual-choice assays using gated-trap vials were conducted in the laboratory to compare SWD adult response to blueberries with and without the volatile compound present in 2-choice assays after a 24-hour period.
From these multiple-choice and 2-choice studies, two compounds (ethyl butyrate and ethyl coronate) were selected for additional testing. A dose-response behavioral assay was conducted in 2-choice arenas to test the repellency to SWD adults of blueberry fruits with and without each of the repellents present under laboratory conditions. The number of flies present in each gated-trap vial and the number of eggs laid in fruits were counted after 2 hours. In addition, electroantennogram (EAG) assays were conducted to determine the response of SWD antennae to the two anthracnose repellents across a concentration gradient. For EAG assays, volatiles were diluted in hexane and compared to a hexane-only control.
In the summer of 2023, caged studies were conducted in the field using potted blueberry plants to test the repellency of ethyl butyrate and ethyl coronate in sachets to adult SWD. Tomato cages were placed over each bush and 5 clusters of ~10 berries were hung randomly around the cage. Fifty adults (1:1 M:F) were introduced into cages and after 24 hours berries were collected and inspected for the number of eggs laid. Berries were further incubated to count adult emergence.
Methyl Benzoate and Analogs
Choice assays were conducted using methyl benzoate and nine of its analogs under laboratory conditions. Assays were compared to a known repellent, Geosmin. Assays used treated blueberries and adult SWD to test for repellency and ovipositional deterrent capabilities. Adult emergence from berries was recorded after 14 days.
Cages were placed in a blueberry field at the P.E. Marucci Center for Blueberry and Cranberry Research (Chatsworth, NJ). Each cage contained a bush and, on either side, treated and untreated blueberries were placed inside. Adult SWD were introduced to the cage and after 24 hours berries were inspected for eggs. Berries were then held for 14 additional days after which adult emergence was taken.
An on-farm field study was conducted to test a push-pull system using methyl benzoate as the push and yellow vane traps with an attractant and a soapy-water drowning solution as a pull. All non-pull plots received a yellow vane trap without the attractant to rule-out the trap presence as an attractant. The study was conducted as a randomized complete block design for a duration of four weeks. After a week, berries were collected from each plot and traps were checked for presence of flies. Berries were checked for presence of SWD eggs and incubated to determine adult emergence.
Elicitors of Plant Defenses
Three crop bioactivators (Actigard, Lifegard, and Regalia) and one crop sterilant (Oxidate) were applied directly to fruits in both semi-field and large cage trials to test the hypothesis that applying elicitors or sterilants can induce changes in the fruits that will ultimately repel or deter SWD adults.
In the semi-field trials, berry clusters (‘Bluecrop’ variety) were contained in fabric bags prior to ripening to prevent infestation. Once the berries were ripe, the clusters were sprayed inside of the bags. Treated berries were collected 1, 3, 7, and 10 days after treatment. These berries were set up in laboratory assays to determine oviposition (in choice and no-choice assays) and attraction at different periods after treatment.
In the large cage field trials, four replicates of each treatment plus a blank control were tested. Five blueberry bushes (‘Duke’ variety) were contained inside each cage. The fruits on these bushes were sprayed thoroughly with each treatment (until dripping). 100 flies (1:1, M:F) were released into the cages 24 hours after treatment. Fruits were collected 3, 7, and 10 days after treatment and were incubated for two weeks to monitor for adult emergence.
Conclusions are based on laboratory, semi-field, caged field trials and thus no recommendations can be made at this time. Further field testing will be needed to test for improved deployment methods and optimal field rates of repellents. Despite this, we have made substantial progress towards the identification of potential novel repellent and oviposition-deterrent compounds for SWD.
Fungal Pathogens
Fourteen compounds were identified from anthracnose-infected blueberries. Initial experiments indicate that nine of the compounds demonstrate repellent properties. Dose-response studies were conducted with two of these compounds: ethyl butyrate and ethyl coronate. These compounds were tested in field cages in the 2023 season.
In 2-choice assays of the nine identified repellents showed that two compounds (ethyl butyrate and ethyl crotonate) had greater than 90% repellency. These two compounds were selected for further laboratory and cage studies.
Dose response of SWD adults to the two compounds showed that both repellents had a dose-dependent effect on SWD. When a 1:1 mixture of the compounds was tested, no dose-dependence effects were observed. Similarly, the compounds individually showed a strong dose-dependent response that was comparable to a known SWD repellent, 2-pentylfuran.
Field testing of the two novel repellents in cages alongside 2-pentylfuran showed that they elicit a reduction in the number of eggs laid per berry that was similar across compounds. As observed in the dose response, a 1:1 blend of the two novel compounds did reduce oviposition but was not different from any of the compounds tested individually. A repellency index (Control-Volatile/Total) showed a similar pattern as the egg counts with individual compounds having a similar repellent effect as the blend.
Methyl Benzoate and Analogs
From the compounds tested, one performed similarly to Geosmin and another exhibited some repellent properties. Further behavioral and toxicity assays were conducted with selected compounds in the laboratory and in the field for the 2023 season. In addition, methyl benzoate was used in combination with baited traps to test the efficacy of push-pull systems for SWD management in blueberry fields.
Berries from ‘push’-only and ‘push-pull’ plots had a smaller proportion of berries with SWD eggs present. These plots also had a lower number of eggs per berry as compared to treatments without a ‘push.’ Only baited yellow-vane traps collected SWD adults, but the ‘pull’-only plots did not have significant reductions in proportion of berries with eggs and number of eggs per berry, indicating it is not as effective alone.
Elicitors of Plant Defenses
The effectiveness of plant activators was inconclusive in both semi-field and field cage experiments. Due to these findings, no tests will be conducted using these elicitors in the future.
Education & Outreach Activities and Participation Summary
Educational activities:
Participation Summary:
Presentations at Scientific Meetings
The results from this study were presented at 4 separate national and international scientific meetings: the 2022 Joint Annual Meeting of the Entomological Society of America (ESA), Entomological Society of Canada (ESC), and the Entomological Society of British Columbia (ESBC), the 2023 Eastern Branch Meeting of the Entomological Society of America (ESA), the 38th Annual Meeting of the International Society of Chemical Ecology, and the 2023 Annual Meeting of the Entomological Society of America (ESA).
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)
Information Products
- Evaluation of a Push–Pull Strategy for Spotted-Wing Drosophila Management in Highbush Blueberry (Peer-reviewed Journal Article)
- Blueberries infected with the fungal pathogen Colletotrichum fioriniae release odors that repel Drosophila suzukii (Peer-reviewed Journal Article)