WERA1021: Spotted Wing Drosophila Biology, Ecology, and Management
(Multistate Research Coordinating Committee and Information Exchange Group)
WERA1021: Spotted Wing Drosophila Biology, Ecology, and Management
Duration: 10/01/2022 to 09/30/2027
Statement of Issues and Justification
Spotted-wing drosophila (SWD) Drosophila suzukii (Matsumura) was first detected in the US in 2008, and over the last decade has become established nationwide. Native to eastern Asia, it is now found in the United States, Canada, Mexico, Europe, and most recently South America (Walsh et al. 2011, Asplen et al. 2015). It is now the most significant pest of blueberries, blackberries, raspberries, strawberries, and cherries (sweet and tart), which have a combined annual value of more than $5.8 billion (USDA NASS 2018), and national crop loss due to SWD has been estimated at up to $718 million annually (Bolda et al. 2010, Farnsworth et al. 2017). Female SWD use their saw-like ovipositor to penetrate the skin of ripe or unripe fruit (Walsh et al. 2011). In addition, SWD is a particularly challenging pest to manage because it has exceptionally high reproductive capacity, and until now, a lack of effective resident biological controls. SWD also has an expansive host range including the utilization of a large number of wild hosts in the surrounding landscape from which they can readily migrate into crop fields (Lee et al. 2015, Elsensohn and Loeb 2018). There is zero tolerance for infestation in fresh fruit, so management programs rely on broad-spectrum insecticides (Bruck et al. 2011, Van Timmeren and Isaacs 2013, Diepenbrock et al. 2016, Smirle et al. 2017). In some crops, insecticide applications have doubled since the SWD invasion, and late-season sweet cherries and berries report requiring as many as 11-16 additional insecticide applications to harvest a marketable crop. There are significant non-target effects of intensive management for SWD, including secondary pest outbreaks due to insecticides disrupting the biological control of other pests. For some pollinator-dependent crops such as fall raspberry, where plants are flowering at the same time that susceptible ripe fruit is present, there are also concerns regarding non-target impacts on pollination services. Due to the intensive use of insecticides, resistance, primarily to spinosad, has already been documented in California (Gress and Zalom 2019). The potential for resistance in other states is high.
Current practices have also resulted in reduced access to export markets because of insecticide residues exceeding maximum limits. These impacts further increase costs of production and result in major logistical challenges. Managing SWD has increased farm labor and input costs, and reduced profitability (Asplen et al. 2015). Insecticide costs have increased by $480-$1,200 per acre in CA raspberries (Farnsworth et al. 2017). Specialty crops employ 68% of all agricultural workers in the USA, and therefore increased insecticide use for SWD management increases the potential for human exposure to these toxic insecticides. Due to the fact that multiple cropping systems and climatic regions are impacted by SWD, and given the severity and scope of losses due to SWD, a multi-state approach and coordination on the management of this pest is warranted.
Comprehensive reviews summarizing recent advances in the management of SWD have been conducted by Tait et al. (2021), with specific reviews on biological and cultural control being conducted by Lee et al. (2019) and Schöneberg et al. (2021) respectively. These approaches are desirable given their potential to reduce insecticide inputs and the related economic and environmental costs. The prospect for greater biological control has been bolstered by successful exploration of parasitoids for SWD in Asia (Daane et al. 2016, Giorgini et al. 2019). The samba wasp, Ganaspis brasiliensis (Ihering) was selected based on its specificity and performance (Wang et al. 2019), and ability to parasitize up to 76% of SWD in fruits in China and Japan (Girod et al. 2018, Giorgini et al. 2019). In October 2021, G. brasiliensis (lineage G1) was authorized for release in the United States.
Research into cultural controls for SWD have focused on preventative tactics such as crop selection and exclusion, as well as, strategies to reduce habitat favorability (pruning, mulching, irrigation), alter resource availability (harvest timing and frequency; sanitation), and lower suitability of fruit postharvest (cooling) (Schöneberg et al. 2021). However, variables such as climate, horticultural practices, crop, and markets underlie the efficacy, feasibility, and affordability of cultural control tactics, and impact the potential of these tactics. Importantly, these variables vary greatly across SWD’s range in the US. Finally, a key knowledge gap that still needs to be addressed to facilitate further integration of SWD cultural controls into commercial production is an in-depth economic analysis of the individual tactics across a variety of production systems. This economic analysis will help ensure that the additional costs provide tangible benefits in terms of SWD control, production goals, and farm profit (Schöneberg et al. 2021). Significant development has also been made in behavioral control options including attract-and-kill techniques (Klick et al. 2019) ovipositional attractants (Rossi-Stacconi et al. 2020, Tait et al. 2020) and baits (Noble et al. 2019), all of which have shown promise for the management of SWD, and are currently undergoing registration with the EPA.
Despite substantial research efforts in the decade since its arrival, SWD remains a top research priority for national, regional, and state grower organizations. Research on SWD remains a top priority for many of the regional IPM Centers, and research funding (USDA-SCRI, USDA-OREI, USDA Specialty Crop Block Grant, regional IPM centers, grower funding, etc.) continues to be obtained to study SWD in many regions of the U.S. The purpose of this committee is to foster and facilitate information exchange to ensure that research, extension, and outreach efforts are appropriate, regionally relevant, and disseminated to stakeholders in a timely manner while minimizing redundant efforts. In addition, this committee facilitates the development of new Multi-State and regional research and Extension projects by fostering collaboration and communication among researchers and Extension agents from multiple organizations. Such efforts have enabled members of this group to obtain funding for such projects. This collaboration will support fruit growers, packers, processors, marketers, export agencies, extension personnel, and fruit consumers by helping the production of healthy soft-skinned fruits in an economically and environmentally sustainable way. Stakeholders are regularly engaged in assessing the value of the research, education, and extension efforts of the Coordinating Committee.
Improve our understanding of SWD populations and develop tools to accurately predict SWD risk to various crops.
Optimize use of pesticides to reduce reliance upon them, monitor and address the development of resistance, and minimize disruption of beneficial insects.
Develop non-pesticide-based tactics, including biological control, for SWD management and evaluate sustainable management programs to provide best management practices recommendations to stakeholders.
Coordinate grant-funded research and extension efforts to minimize redundancy and ensure knowledge transfer across multiple states and regions.
Procedures and Activities
Objective 1: Improve our understanding of SWD populations and develop tools to accurately predict SWD risk to various crops.
Reliable monitoring of pest populations and ensuring control measures are not taken needlessly, is essential for sustainable pest management. Not only can SWD use a broad range of resources, including many non-crop hosts (Lee et al. 2015, Elsensohn and Loeb 2018), but they also have high reproductive capacity (Emiljanowicz et al. 2014), and develop relatively rapidly (Tochen et al. 2014). Populations build rapidly with generations overlapping early in the season, and current monitoring tools are limited in their ability to predict SWD damage. We will address these knowledge gaps with coordinated multi-state research. To improve our ability to model SWD populations nationally, we will compare regional data on trapping, infestation, and weather across different host crops in order to refine population models. SWD may be moving at local and regional scales between habitats. Molecular tools will be developed that allow for differentiation between long range and local dispersal, understanding this dispersal remains a priority to determine risk of insecticide resistance spread. Experiments will be conducted to track SWD movement and infestation across hosts, determining seasonal, temporal, and spatial usage of, and dispersal among crops and non-crop hosts. We will coordinate efforts to develop monitoring tools and tactics that accurately estimate SWD populations, including studies to improve our understanding of currently available attractants, develop and optimize new attractants, and time treatments based on trapping data.
In addition to adult trapping, direct monitoring for SWD larvae can be conducted using a fruit dunk flotation technique, similar to methods developed for other drosophilid pests (Yee 2014). Recent modifications to this method by growers in different regions allowed for quicker and more accurate detection of SWD eggs and larvae in infested fruit (Van Timmeren et al. 2017, Van Timmeren et al. 2021). Monitoring for fruit infestation has the advantage of providing real-time information that growers can use to adjust insecticide applications and/or harvest schedules. We will continue to coordinate on the optimization and uses of monitoring immature life-stages of SWD to inform management decisions, and anticipate future collaborative proposals to support this work as a result of this project.
Objective 2: Optimize use of insecticides to reduce reliance upon them and minimize disruption of beneficials.
Stakeholders regularly prioritize research to optimize the use of insecticides because current spray programs may not meet their management goals, their desired market, and insecticide resistance is increasingly a concern. Regional production practices and climatic factors such as rainfall, impact efficacy, necessitating multi-state research projects. We will work to widely apply the recently developed RAPID resistance monitoring protocol to monitor for resistance nationally, focusing on numerous active ingredients. To minimize disruption of beneficials, we will continue to screen new insecticides, particularly NOP-compliant and reduced risk insecticides alone and in combination with baits and attract-and-kill technologies for their effects on non-target biological control agents and other beneficials.
Objective 3: Develop non-pesticide-based tactics, including biological control, for SWD management and evaluate sustainable management programs to provide best management practices recommendations to stakeholders.
Currently, both organic and conventional production systems rely heavily upon chemical control tactics to manage SWD, and additional management tactics are desperately needed. Tactics such as biological control, cultural control, antifeedants, non-nutritive baits, and alternative ovipositional attractants will be explored. Regional differences in production practices will impact the efficacy and feasibility of management tactics; therefore, a multi-state approach is warranted. Tactics will be evaluated in laboratory, small plot, and on-farm experiments. The most promising approaches will then be evaluated in coordinated regional field trials to evaluate their efficacy under a range of climatic and production conditions.
This project will also serve to coordinate multiple state-supported projects to rear, release, and evaluate G. brasiliensis. We look forward to expanding our network to include state department of agriculture personnel to facilitate this coordination.
Cooperating with stakeholders in each region, replicated, on-farm research will be performed to evaluate new management tactics for SWD and encourage adoption of IPM programs. Economic analyses of specific management practices and bioeconomic models to identify profit maximizing management strategies will be used to generate research-based recommendations and decision support tools.
Objective 4: Coordinate grant-funded research and extension efforts to minimize redundancy and ensure knowledge transfer.
Because SWD is an economically significant threat nationally, many individuals are performing research, extension and outreach efforts. This committee will enhance collaborations and provide opportunities to share information and ideas, facilitating needs assessments, minimizing redundancy, and accelerating the delivery of outputs to stakeholders.
Expected Outcomes and Impacts
- This project will coordinate research and extension efforts, allowing for the exchange of ideas, information, and data thereby accelerating SWD research and extension throughout the U.S. This committee has facilitated the development and funding of multiple Multi-State projects and we anticipate that future regional and Multi-State projects will result from this coordination.
- Regionally appropriate decision support tools will be developed and disseminated to stakeholders, resulting in economic benefits due to improved decision-making. This committee will enable the development and dissemination of improved monitoring and thresholds for SWD, which will allow for judicious use of chemical control strategies and decrease insecticide use for SWD management.
- Regionally appropriate IPM programs will be developed and disseminated to stakeholders, resulting in economic benefits due to improved management tactics and decision-making. Specifically, members of this team are developing tactics that will be incorporated into IPM programs such as cultural control methods, attract-and-kill strategies, exclusion approaches, and targeted chemical control. The adoption of new management practices for SWD will decrease yield losses, increase profitability, and improve sustainability.
- Committee participants will produce complementary and collaborative research articles, thus reducing duplication of efforts while providing timely research-based information and educational materials to research and Extension teams nationally. These efforts will increase the dissemination of information and ensure that stakeholders gain the knowledge and skills they need to successfully manage SWD.
- Timely communication to stakeholders will allow growers and industries to integrate new approaches to mitigate the impact of SWD-related crop losses and will result in more environmentally and economically sustainable fruit production in the USA. The efforts of this committee will increase the adoption of best management practices and IPM approaches for managing SWD.
Projected ParticipationView Appendix E: Participation
At each annual meeting, the committee will present the current year's activities, and then discuss, share, and coordinate SWD management issues, future research and extension needs, extension educational approaches, and novel applications within regional fruit production and home gardener/urban landscape systems. The annual meeting will provide a forum for research and extension liaisons throughout the country to discuss issues and coordinate responses. An annual report will be compiled to provide documentation of regional deliverables and accomplishments in SWD management during the past year. Following the annual meeting, members of the committee will disseminate information gained to appropriate parties within their areas. Extension agents and teams will be updated and trained as needed, workshops and field days will be organized, and educational materials will be shared with grower groups. Throughout the year, members of the committee will share information with each other about what outreach materials and approaches were most and least effective.
During this project, WERA members will organize at least one regional symposium at a branch meeting of the Entomological Society of America, a national symposium at an Annual Meeting of the Entomological Society of America, and at the International Congress of Entomology meeting in 2024 (Japan). These professional activities will: 1) expand information exchange beyond the WERA membership, 2) address specific learning needs, 3) provide professional development to stakeholders, 4) foster inter-agency and regional/national linkages, dialogue, learning, and information dissemination, with an emphasis on designing and implementing sustainable management of SWD. Stakeholder involvement will be strongly encouraged.
The recommended Standard Governance for multistate research activities include the election of a Chair, a Chair-elect, and a Secretary. All officers are to be elected for at least two-year terms to provide continuity. Administrative guidance will be provided by an assigned Administrative Advisor and a NIFA Representative.
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