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Monitoring is a critical part of managing SWD. Dr. Juliet Carroll and her many collaborators from around NY State have been working to provide and improve monitoring since 2013, sharing information from the SWD monitoring network in this blog. Over the past two years, our team has evaluated traps to make monitoring easier. I was fortunate to begin working with this group in 2023, as the new Fruit IPM Coordinator with the NYS IPM Program, and am pleased to summarize the result of the past two years.

As noted in a previous post, monitoring can save unnecessary sprays in a late infestation year, reducing time and labor, decreasing pesticide use, and protecting against pesticide resistance. In an early year it can also ensure adequate protection is in place, and production of high-quality fruit. However, monitoring is time-intensive and requires specialized equipment. Identifying an easier monitoring method is also critical because the SWD-network can only provide county trends, not farm-specific information. Over the past two years, a team across the state compared jar (drowning) traps with red sticky cards, to see if they are as effective at detecting SWD. Thanks to Laura McDermott, who received a Smith-Lever Federal Capacity Fund grant to do this work!

2023 Monitoring Results. In 2023, the SWD monitoring network included 118 monitoring locations in 24 counties, maintained by 18 individuals. First trap captures were reported from June 13-July 20, and sustained captures a week later (sustained capture = SWD detected at least two weeks in a row). This is considerably later than average; in many years, first capture occurs in mid-May, almost a month earlier! 2023 was a brilliant example of how monitoring can be used to delay pesticide applications until insects are present, saving time, labor, and materials.

Traps in the SWD monitoring network are located on commercial farms, and typically serviced by Cornell Extension Personnel or grower collaborators. In addition, some growers have begun servicing their own traps, with our guidance or from reading the online resources.


Are you monitoring for SWD (Spotted Wing Drosophila) on your farm? We'd like to know! Please complete this 6-question survey about your SWD monitoring. https://cornell.ca1.qualtrics.com/jfe/form/SV_2iBzQU9NpKO1WKO


Trap Comparison Methods & Results. Over the 2022 and 2023 growing seasons we compared jar and sticky traps at berry or cherry plantings across New York state. At each site, two of each trap type were placed along the edge of the berry patch or orchard, spaced 50 meters apart. Traps were monitored weekly through sustained trap capture (two consecutive weeks of at least one SWD in the trap) and the number of SWD observed in each trap was recorded.

SWD monitoring traps are available for purchase from Great Lakes IPM: https://www.greatlakesipm.com/product_search/?q=swd 

Jar traps. Scentry jar traps with lure have been used since 2016 in the SWD monitoring network. They require filling a plastic jar trap with a ‘drowning solution’ of soapy water, and attaching a Scentry lure. The trap is placed in the canopy and monitored weekly. Drowning solution must be filtered using a funnel and fine mesh, and its contents is taken to the lab to identify flies under a dissecting microscope. Research has consistently demonstrated that these traps are among the most effective and sensitive for early detection of SWD. However, the process of monitoring is tedious, time-consuming, and requires specialized equipment, and may be too onerous for commercial growers.

Photo 1: A red jar hanging in a raspberry bush. Photo 2: Jar being drained through mesh using a funnel. Photo 3: A ziploc bag containing the mesh. Photo 4: close up image of many small fruit flies clustered together on a white paper.
Figure 1: How to service a jar trap.

Sticky cards. An alterative to jar traps are sticky cards. These red cards are affixed in the canopy along with a Trécé scented lure, and are monitored weekly for SWD. The cards are examined for male SWD in the field, which are easy to identify using a hand lens or optivisor, by the characteristic spots on the tips of the wings.

Photo 1: Red sticky card in blueberry bush. Photo 2: Close up of card with dark black insects stuck to it. Photo 3: New red sticky card with white paper backing being peeled off. Photo 5: sticky card being placed in ziploc bag. Photo 5: New Red Sticky card and lure hanging in bush.
Figure 2. How to hang a sticky red card with lure. Credit: J. Carroll.

In 2022, jar and sticky trap detection dates were the same at 6 of 19 locations (31.6%), jar traps were earlier at 9 locations (47.4%), sticky traps were earlier at 2 locations (10.5%), and at 2 locations SWD was not detected (10.5%). In 2023, detection was the same for trap types at 5 of 17 locations (29.4%), jar traps were earlier at 8 locations (47.1%), sticky traps were earlier at 3 locations (17.6%), and at 1 location SWD was not detected (5.6%). Our results indicate that jar traps may detect SWD earlier than sticky traps a slightly larger proportion of the time, as long as monitoring is conducted correctly by a trained individual with access to appropriate tools. However, sticky traps detected SWD earlier at many locations, and required considerably lower input.

Two bar graphs comparing Jar Traps vs. Sticky cards, and which detected SWD earlier. Top is 2022, Bottom is 2023. Both show the Percent of traps on the y-axis. Four bars include Same Date, Jar Traps Earlier, Sticky Card Earlier, and No SWD Capture. the first and second bar are highest in both graphs.

 

We believe the two trap types offer a similar level of detection and that user preference likely plays a large role in the successful implementation. Having multiple trap types available is likely to increase the practice of monitoring, thus site-specific detection of SWD and targeted pesticide use to reduce fruit infestation and other negative consequences. Further improvements to the sticky traps (grid lines, yellow color) may make improve user-friendliness (and therefore detection) and will be evaluated in the future.

Our results in 2022 and 2023 are consistent with preliminary work in 2021 in NY, and with what teams are finding in other locations. Preliminary trials in 2021 in NY included 20 sites, in which first trap catch was compared for Scentry-lure-baited jar traps vs. Trécé -lure-baited red sticky cards. “First catch on the red sticky cards compared to the jar traps was about one week earlier at 40% of the trap locations (8 out of 20), about one week later at 45% of the locations (9 out of 20) and on the same date at 15% of the locations (3 out of 20).” This suggested that the red sticky cards work comparably to the jar traps.

The Sustainable SWD Management Team has over two years of data from locations across the country indicating that jar traps and red sticky cards offer comparable efficacy and sensitivity for early detection of SWD. Research evaluating these and other monitoring devices is ongoing. A webinar summarizing research updates on monitoring tools was shared in 2021. In addition, our colleagues in Ontario have been testing yellow sticky card traps, which may make it easier to see insects. They have been testing with and without cages, which prevent messy buildup of debris and capture of non-targets. Their results from two years of research indicate that yellow sticky cards may be as effective as red cards, and that round cages (but not flat “sleeve” cages) are effective at keeping cards clean and detecting SWD. In 2024 our team plans to include tests comparing these yellow cards to the other types of traps in NY.

Photos of yellow sticky cards hanging in a bush with a round mesh cage around it.
Yellow sticky card in round cage. Photo: Erica Pate and Hannah Fraser, OMAFRA.

 

Acknowledgements. I’d like to extend a huge thanks to Dr. Juliet Carroll and the many collaborators around NY state who have provided support for SWD in this trap comparison project for the past three years, as well as the monitoring network and blog since 2013!

2023 Collaborators:

Amy Edwards, Burdick Blueberries
Anya Osatuke, Harvest New York, CCE
Dan Gilrein, Suffolk County CCE
Don Gasiewicz, Wyoming County CCE
Elisabeth Hodgdon, ENYCHP, CCE
Elizabeth Tee, Lake Ontario Fruit Program (LOF), CCE
Gary Phelps, Gary’s Berries
James O'Connell, Ulster County CCE
Janet van Zoeren, Lake Ontario Fruit Program (LOF), CCE
Jared Dyer, Suffolk County CCE
Jennifer Staton, ENYCHP, CCE
Jonny Williams, Northstar Blueberry Farm
Laura McDermott, ENYCHP, CCE
Natasha Field, ENYCHP, CCE
Nick Hamilton-Honey, CCE

Support for this work was provided by the NYS Berry Growers Association, the NYS IPM Program, and the USDA NIFA CPPM EIP Award 2017-70006-27142.

Sustainable SWD Management swdmanagement.org/

- Anna Wallis, Fruit IPM Coordinator, NYS IPM Program

This blog was co-authored by Laura McDermott, Janet van Zoeren, and Anya Osatuke. Eastern NY Commercial Horticulture Program, Lake Ontario Fruit Program, and Harvest NY, respectively, all with Cornell Cooperative Extension.  

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On Thursday, March 10, 2022, from 11:30 to 12:30, I will present our work on using hummingbird feeders to attract Ruby-throated Hummingbirds into raspberry plantings as an aid in managing SWD. This seminar will be part of the NYS IPM Program's Seminar Series. To learn more about the NYS IPM Seminar series and upcoming talks, visit nysipm.cornell.edu/resources/nysipm-seminars/.

My seminar will be presented via zoom, so you can join and watch from the comfort of your home office or wherever you are using this zoom link:

cornell.zoom.us/j/97142846187?pwd=c0hNbldOR3ZXbFF0eVgzc2YybUMzUT09 https://cornell.zoom.us/j/97142846187?pwd=c0hNbldOR3ZXbFF0eVgzc2YybUMzUT09

Here is a summary of our work on hummingbirds, which I will present on March 10, 2022 at 11:30 to 12:30.

Hummingbirds require arthropods in their diet and may consume 2000 small insects, including Drosophilids, per day when fledging young. In New York State, we investigated the use of feeders to attract Ruby-throated Hummingbirds into raspberry fields to encourage predation of spotted-wing Drosophila (SWD) with the goal of reducing fly populations and fruit infestation. Baited traps were used to assess fly populations and salt flotation was used to assess fruit infestation. Over four years (2015-2018), 81% of 266 hourly observations of hummingbird behavior found the birds were occupying the raspberry planting when utilizing the feeders, supporting opportunities for predation on SWD flies. In 16 out of 18 weeks in 2017 and 2018, the number of SWD found in fruit were reduced in the half of the field with 62 feeders/hectare (25/A), compared to the half without feeders. We found a significant season-long reduction of 27% in average fruit infestation in 2017, a year with high populations of SWD. Trap catch was lower in the feeder half of the field in 15 of 25 weeks in 2016-2018. In two 0.035 ha (0.09 A) commercial raspberry fields (2020), in the one with 151 feeders/hectare (54/A) significant reductions in trap catch were found in most weeks during the fruiting season compared to the field without feeders. No Ruby-throated Hummingbirds were observed in the commercial field without feeders. Hummingbirds may protect fruit against SWD when encouraged with feeders to visit and occupy raspberry plantings.  Encouraging hummingbirds in raspberry fields with feeders has the potential for contributing to an SWD IPM program and reducing the reliance on chemical management.

A Ruby-throated Hummingbird.
Hummingbirds eat lots of small insects, including aphids and fruit flies to supplement their nectar-rich diet, up to 2000 per day!

Want to learn more about how to use hummingbird feeders in your raspberry plantings? Contact Juliet Carroll, jec3@cornell.edu, Fruit IPM Coordinator, NYS IPM Program, Cornell University. Collaborators on this project included: Percival M. Marshall, NYS IPM Program, Nicole E. Mattoon, NYS IPM Program, Courtney A. Weber, Horticulture, and Greg M. Loeb, Entomology.

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Spotted-wing drosophila monitoring helps to determine when populations begin to build up, and can help save growers' spray applications in a late infestation year. In 2021, we tested red sticky card traps, baited with SWD lures, to detect first arrival of SWD in berry plantings and cherry orchards. The baited, red sticky traps provided good results for the SWD monitoring network. We found that the red sticky traps have potential for use by growers and consultants to monitor SWD pressure in at-risk fruit plantings. The exciting news is that Laura McDermott, ENYCHP, obtained grant funding to further test the red sticky traps and to lead a statewide effort to educate growers and consultants on their use.

SWD monitoring recap:
The 2021 statewide monitoring effort included 126 trap locations monitored by 16 Cornell extension scientists in 23 counties. During the season, first trap catch across the SWD monitoring network occurred over a 14-week-long period, from May 11 (Niagara County) to August 17 (Steuben County). The occurrence of first catch over several weeks is typical for SWD occurrence in New York State. However, most trapping sites were not catching SWD during the late May and early to mid-June period, and only one reached sustained catch in early June. Normally, by mid-June, most traps will have caught SWD.

Scentry jar trap
Scentry jar trap for SWD set in a raspberry patch.

Scentry jar traps with lure have been used in the SWD monitoring network since 2016. Lured jar traps from which SWD are filtered, sorted from related species, then identified with magnification are currently the best at attracting the first insects, but growers cannot implement this level of monitoring and the statewide trap network isn’t robust enough to deliver farm-specific information. Using an easier monitoring method, if it works as well as the jar traps, will help growers monitor SWD on their own farms. Growers in New Jersey and Ontario, Canada have successfully used red sticky card traps with lures to monitor SWD on their farms.

Sticky card trap results:
Cornell extension scientists in the SWD monitoring network conducted a preliminary test in 2021 of the use of red sticky card traps. A total of 20 locations, where both the Scentry-lure-baited jar traps and the Trécé-lure-baited red sticky card traps were being used, yielded data to compare the first trap catch date for the jar traps and the red sticky card traps. First catch on the red sticky cards compared to the jar traps was about one week earlier at 40% of the trap locations (8 out of 20), about one week later at 45% of the locations (9 out of 20) and on the same date at 15% of the locations (3 out of 20) . These results suggest that the red sticky cards will work comparably to the jar traps and that using sticky traps won’t lead to trap catch results being obtained too late, which would place crops at possible risk of infestation from populations of SWD that have gone undetected.

Trap comparison chart
Comparison of first SWD catch in Trécé-lure-baited red sticky card traps versus Scentry-lure-baited jar traps.

Setting up sticky cards:
The red sticky cards are relatively easy to use, though the sticky coating on the traps can pose a challenge for the user. Wearing nitrile, latex, or plastic disposable gloves to protect hands from the sticky goo on the trap is essential. Tying back long hair can be helpful. An SWD lure is positioned above the red sticky card, which is hung from a branch, trellis wire or wooden stake, preferably 1.5 m (5 ft.) off the ground, and within the fruit zone in a shaded area. In berries, this will depend on how the plants are trained and traps may need to be placed lower. Traps must be secured tightly to the trellis wire, branch, or wooden stake to minimize sliding or blowing around with the wind or the airblast sprayer. Canes or branches should be tied up or removed so the sticky traps are easily seen and won’t contact any foliage or berries. Mark the location of the trap with flagging tape. Label the trap with a code number for your records. Record the date the trap and lure were set out in the field and the trap GPS coordinates, if needed.

Setting up red sticky cards.
The steps for hanging the lure and red sticky cards.

SWD identification

Reading the sticky cards:
It is easy to identify the male flies, because they have the distinctive oval spot on each wing. To service the trap and identify the male SWD, again, it is best to wear gloves and tie back long hair to protect yourself from the sticky goo. Each week, remove the trap and check for stuck male SWD. Examine both sides of the sticky trap with a hand lens, magnifying glass or OptiVisor DA 7 (2.7x magnification) or DA 10 (3.5x). Enumerate the male SWD caught on both sides of the sticky card and record the total number per red sticky card trap. Discard the examined trap and install a new one. It is very important to change the trap weekly when you check for SWD. This will make it much easier to identify insects. Change the lure every 4 weeks and make note of the date the lure was changed.

Reading sticky cards.
The steps for servicing the red sticky card traps in the field.
OptiVisor use
Deborah Breth, Lake Ontario Fruit Team, retired, examining fruit using an OptiVisor. A hand lens is shown hanging from a lanyard around her neck.

Future plans:
The two-year grant paves the way for further testing the red sticky card traps and educating growers and consultants on their use. This project is getting started in spring 2022. It will entail grower and consultant demonstrations, extension materials, and education efforts on the use of red sticky cards baited with SWD lures, to monitor for SWD in berry plantings and cherry orchards.

SWD males on red sticky card trap
Male SWD, circled in yellow, can be readily detected on red sticky card traps.

Acknowledgements:
We want to thank the collaborators on the 2021 SWD monitoring network, many of whom tested the red sticky cards.
Andy Galimberti, ENYCHP, CCE
Ariel Kirk, Steuben County CCE
Barb Neal, Tioga County CCE
Dave Thorp, Livingston County
Don Gasiewicz, Wyoming County CCE
Elisabeth Hodgdon, ENYCHP, CCE
Elizabeth Tee, Lake Ontario Fruit Program (LOF), CCE
Faruque Zaman, Suffolk County CCE
James O'Connell, Ulster County CCE
Liz Alexander, Chemung County CCE
Natasha Field, ENYCHP, CCE
Sarah Tobin, ENYCHP, CCE

Support for this work was provided by the NYS Berry Growers Association, the NYS IPM Program, and the USDA NIFA CPPM EIP Award 2017-70006-27142.

This blog was co-authored by Laura McDermott, Janet van Zoeren, and Anya Osatuke. Eastern NY Commercial Horticulture Program, Lake Ontario Fruit Program, and Harvest NY, respectively, all with Cornell Cooperative Extension.  

Data from 10 years of trapping for first catch of SWD, posted below, shows a trend towards earlier first arrival of SWD into fruit plantings. During the 2021 season, first trap catch occurred over a 14-week-long period, May 11 (Niagara County) to August 17 (Steuben County). This year we tested the utility of red sticky cards, baited with SWD lures. The SWD team achieved another year of successful SWD monitoring! Please join me in thanking the 15 extension scientists who contributed to this effort across 23 counties. Growers in and outside the network locations rely on this information to alert them about the need to protect their at-risk fruits crops from SWD infestation as harvests draw near.

Earlier first trap catch

First trap catch date trend.From the initial year of trapping for SWD, in 2012, we have seen a trend for first trap catch to be earlier, 76 days earlier. Other northern states with trapping programs have noticed this trend. Could it be SWD is adapting to our climate and more adults are surviving the winters? Could it be related to climate change and milder winters or autumns with fewer early freeze events? Or are the trap lures simply getting better?

Asynchronous first trap catch

2021 SWD first catch map
Map showing first catch months for counties having traps. Counties colored white have no traps.

Where was SWD during late May and early to mid-June? We don’t know. Most trapping sites weren’t catching SWD during this period, and only one reached sustained catch in early June. “Normally” (is there a normal?) by mid-June, many traps will have caught SWD. Were the lures off? Not the case, we were using both Scentry (in jar traps) and Trece (with sticky cards) lures and these traps, from a quick perusal of my data, yielded comparable results. Perhaps simply another puzzle for researchers to ponder over — weather effects?, natural enemies?, spray programs?

Baited red sticky cards

SWD males on red sticky card trap
Male SWD can be detected readily on red sticky card traps.

We achieved success with the red sticky cards, though deployment and use of the cards can be tricky. Stay tuned for more information on this in a future blog. Laura McDermott will be leading a two-year project to work more with these types of SWD traps and educate growers and consultants on their use.

Now, on to thanking everyone!

These 15 Cornell University extension scientists participated in SWD monitoring this year in 23 counties. A special thanks go out to them for setting traps, changing lures, servicing traps, and identifying SWD. This network would not be possible without their support and contributions — suggestions for improvement, ideas for mapping, perspectives on grower needs and steadfast cooperation.

  • Andy Galimberti, Eastern NY Commercial Hort Program
  • Ariel Kirk, Steuben County CCE
  • Barb Neal, Tioga County CCE
  • Dave Thorp, Livingston County
  • Don Gasiewicz, Wyoming County CCE
  • Elisabeth Hodgdon, Eastern NY Commercial Hort Program
  • Elizabeth Tee, Lake Ontario Fruit Program
  • Faruque Zaman, Suffolk County CCE
  • Janet van Zoeren, Lake Ontario Fruit Program
  • Jim O'Connell, Ulster County CCE
  • Juliet Carroll, NYS IPM Program
  • Laura McDermott, Eastern NY Commercial Hort Program
  • Liz Alexander, Chemung County CCE
  • Natasha Field, Eastern NY Commercial Hort Program
  • Sarah Tobin, Eastern NY Commercial Hort Program

Most importantly, we acknowledge the support of our funding partners:

  • NYS Berry Growers Association
  • NYS IPM Program
  • USDA NIFA CPPM EIP Award 2017-70006-27142

Thank you all!

Growers! You know what you need to do to keep your fruit healthy and free of SWD infestation! If you need a refresher, review the information on the Cornell Fruit Resources SWD management web pagefruit.cornell.edu/spottedwing/management/, and learn more about SWD's life cycle on the Cornell Fruit Resources SWD biology and life cycle web pagefruit.cornell.edu/spottedwing/biology-and-life-cycle/ to better understand how infestations, once started, can ramp up.

There are may things you can do in the “off” season to make your fruit plantings less susceptible to SWD. Wishing you successful harvests!

Another early catch of a single SWD, this time a female, on Monday, May 17, 2021. She was relatively small and her abdomen didn't appear to be full of eggs, though no dissections were done post-mortem to verify this. Three other traps in the orchard, all had zero SWD. Because traps were set on May 10, no zero catch was obtained in this block in Wayne County. This site is being monitored by Juliet Carroll, IPM, as part of a research project on SWD in tart cherry.

Tart cherry orchard with honeybee hives.
It's May 17, 2021 and different levels of bloom can be seen on trees in this tart cherry orchard in Wayne County where honeybee hives are still set out for pollination of the cherries and nearby apple orchards, many which are in full bloom, depending on the variety.

The orchards in Wayne County were at various phenological stages, due possibly to the period of cold, rainy weather in late April to early May delaying the progression of bloom. 50% bloom to petal fall stages were noted, sometimes within the same orchard block.

Obviously, without fruit the risk of fruit infestation from SWD is zero. And, hopefully, the current hot, dry weather trend may slow SWD development.

This past season, 2020, we found a significant reduction of SWD in a raspberry planting using hummingbird feeders to attract ruby-throated hummingbirds into the planting.

In addition to nectar, ruby-throated hummingbirds feed on small, soft-bodied insects, snatching them directly out of the air or pulling them off plants. Early studies of hummingbirds raised in aviaries in Germany (Scheithauer 1967) used Drosophila melanogaster, the common fruit fly, to supplement their diet, without which they failed to thrive, proving unequivocally that hummingbirds require arthropods in their diet. If they can capture and eat D. melanogaster, it is certain that they can capture and eat D. suzukii, SWD. But will it help fruit growers?

A photo of a ruby-throated hummingbird in flight.
Hummingbirds eat lots of small insects, including aphids and fruit flies to supplement their nectar-rich diet, up to 2000 per day!

Hummingbirds are known to learn how to find and use new food resources. They aren't picky eaters — eating small spiders, gnats, aphids, fruit flies, etc. Scheithauer (1967) even noted the behavior of hummingbirds to "buzz" the fruit flies to fan them off the surface they had settled onto. Once in the air, the hummingbird chased after an individual fruit fly until catching it and devouring it. Ruby-throats have been clocked at over 25 mph! And they can turn on a dime, which is about how much they weigh.

In western NY, one raspberry farm and one blueberry farm are actively utilizing hummingbird feeders in their operations (25 feeders/acre) as a management tactic for SWD. In 2020, plots on these farms were compared to plots on two others that did not use feeders to get at whether the feeders were helping against SWD.

The raspberry plots were on conventional farms and the floricane varieties were unknown. The raspberry farm without feeders was U-pick and implemented a conventional spray program, beginning when SWD was caught in traps and fruit were ripe. The raspberry farm using feeders was a CSA and did not apply insecticides.

The blueberry plots were on organic farms and both contained ‘Blueray’ (two rows) and ‘Bluecrop’ (one row). The organic blueberry farm without feeders was U-pick direct market and relied on sanitation and clean picking to manage SWD. The organic blueberry farm using feeders was direct market and used a single application of spinosad (Entrust) followed by a single application of pyrethrin (Pyganic) at labeled rates once SWD was caught and fruit were ripe.

Four rows, each 35.4 m (116 ft) long, were used for the experiment at each farm. Assessments for SWD were conducted in three of the four rows, one on the edge and two in the interior of the planting. Adult fly abundance was assessed weekly with Scentry SWD traps and lures. Samples of marketable fruits collected from each plot were assessed for fruit infestation using salt flotation to enumerate SWD larvae per gram of fruit using the method described by Van Timmeren et al. (2017).

A photo showing a ruby-throated hummingbird at a feeder set in a blueberry planting.
Female or young ruby-throated hummingbird on a feeder set above a blueberry planting.

Hummingbirds were seen at all observation time points from June through August in the berry plantings using feeders. None were seen in the plantings without feeders.

In 8 of 11 weeks, the raspberry plot with hummingbird feeders had statistically fewer SWD than the plot without feeders, especially in the latter half of the growing season. No statistical differences were observed in the SWD numbers between the blueberry plots.

Differences were seen in the fruit infestation levels in the raspberry plots with lower infestation in the plot with feeders. No differences were found between the blueberry plots in fruit infestation levels. In all farms, SWD fruit infestation levels were low in the marketable fruit samples collected: 0 to 0.78 larvae/g of fruit in blueberry and 0 to 0.04 larvae/g in raspberry.

We are currently preparing a manuscript for publication of this work and the prior field research experiments. The 4-year study in research plots was summarized in a Fruit Quarterly article (Carroll et al. 2020). The Spring issue (see page 9) is available at https://nyshs.org/wp-content/uploads/2020/06/NYFQ-BOOK-Spring-2020_FINAL.pdf

The investigation of ruby-throated hummingbird predation of SWD in grower fields was done by Juliet Carroll and Grace Marshall, NYS IPM Program, with advice and guidance from Courtney Weber, Section of Horticulture and Greg Loeb, Department of Entomology. We are located at Cornell University, Cornell AgriTech, Geneva, NY

Funding to support this work has been provided by the New York State Berry Growers Association and the USDA NIFA CPPM EIP award 2017-70006-27142.

Literature cited:

Carroll, J., Weber, C., and Loeb, G. 2020. Hummingbirds can reduce spotted wing drosophila (SWD) fruit infestation. Fruit Quarterly 28(1): 9-13.

Scheithauer, W. 1967. Hummingbirds: flying jewels. Translated by G. Vevers. Arthur Barker Ltd and Thomas Y. Crowell Co., NY. 176 pp.

Van Timmeren, S., Diepenbrock, L. M., Bertone, M. A., Burrack, H. J., and Isaacs, R. 2017. A filter method for improved monitoring of Drosophila suzukii  (Diptera: Drosophilidae) larvae in fruit. J. Integr. Pest Manag. 8: 1-7.

On December 8th, a nation-wide team of scientists presented a webinar, organized by Dr. Hannah Burrack from NC State, on the past ten years research findings related to spotted wing drosophila (SWD) management. The entire 1.5-hour webinar recording can be viewed by anyone — you can access it on the Sustainable Spotted Wing Drosophila Management, swdmanagement.org/, webpage or watch it on YouTube, A Decade of SWD: Lessons for Management at youtu.be/Rk-e13Gov24. Some of the key takeaway messages I found most of interest are described below.

Dr. Greg Loeb from Cornell University presented on the seasonal phenology of SWD. As we’ve emphasized, and you have probably seen in your own operations, SWD doesn’t arrive in traps or orchards early in the spring. They generally show up in our region around mid-June, and populations continue to build through to harvest. Dr. Loeb presented findings from several preliminary studies looking at the best timing for the most efficacious insecticides, which show that best control comes from using the best materials early in the season (when populations are low, and you can best delay the population spike), and rotating to softer products later, closer to harvest. Remember that you can find an updated insecticide efficacy chart on the Cornell Fruit Resources SWD webpage fruit.cornell.edu/spottedwing/management/.

Dr. Phil Fanning from the University of Maine presented preliminary data on the use of a feeding stimulant – to see if adding something “tasty” to an insecticide application would encourage SWD adults to feed more, and increase the efficacy of the insecticide. Although these were found to work moderately well in the lab for some insecticides (especially acetamiprid), preliminary results show it to not be effective in the field, at this time.

Dr. Kent Daane from the University of California presented information on the potential for classical biological control (bringing natural enemies from SWD’s native range to introduce in the USA). This is, of course, a complex decision to make, since we want to be very careful not to introduce a new species that may cause problems of its own! However, native natural enemies seem to be very ineffective at controlling SWD, so classical biocontrol would be the best option, if it can be done safely. At this point, there are two candidate parasitoid wasps that have been thoroughly researched and have been shown to not cause “non-target” effects on other native flies or insects. If all goes well, they could move into the permitting stage in 2021, and be available for release in the next year or two!

Dr. Ash Sial from the University of Georgia summarized the most effective cultural control practices:

  1. The ideal harvest frequency has been found to be 2-day intervals, in order to maximize control while minimizing unnecessary time spent harvesting.
  2. Increased pruning and use of drip irrigation can make your planting less attractive to SWD.
  3. Mulch that creates a complete physical barrier (i.e. weed fabric or mylar) reduces SWD pupation.
  4. Exclusion mesh with <1mm holes has a very high initial cost, but can lead to 100% control when done well.

Dr. Cesar Rodriguez-Saona from Rutgers University discussed Attract and Kill technologies, which show potential in research trials, but still need more data before they would be ready to be implemented.

Dr. Vaughn Walton discussed Sterile Insect Technique, which is still in the field research stage, and would have a long development and regulatory process to go through before it could be available for commercial use.

Finally, I’m excited to announce that Dr. Larry Gut, from Michigan State University, will be presenting on his SWD research at our upcoming Winter Tree Fruit Conference on February 2nd! Dr. Gut specializes in tree fruit entomology, and he will be discussing a degree day model for SWD infestation that his lab has been developing, to help track more specifically the best timing for utilizing your best chemistries to control SWD, among other SWD management recommendations. I hope you’ll be able to attend!

This blog was contributed by Janet van Zoeren, tree fruit and berry IPM specialist, Lake Ontario Fruit Program, Cornell Cooperative Extension. Contect her at jev67@cornell.edu. Sign up for their newsletter and become a member of their Regional CCE Program. Find out more at CFR CCE Newsletters webpage fruit.cornell.edu/newsletters/.

As I sat one evening enjoying my glass of Cabernet Sauvignon on my patio in the Finger Lakes, I noticed several small fruit flies flitting about my wine. Hmmmm...yes, SWD. The tell-tale spots on the wings of the males were a dead giveaway. And I've grown so used to the golden brown somewhat hunchbacked body of the females, that I knew who they were. Red wine is known to be highly attractive to SWD, as is Concord grape juice. Both have been used as baits and drowning solutions in SWD traps. Although, I'd rather not waste wine in an insect trap.

Photo of an SWD on a wine glass.
SWD on a wine glass can ruin your summer evening.

This week Grace Marshall and I are doing a final check of the traps we have in our research plots. Last week, on average, we were catching 20 to 1000 SWD per trap in the summer raspberry and blueberry plantings with nary a fruit in sight. Counting the SWD in those traps is no small task. I was finding myself seeing spots — literally, SWD wing spots — the day after counting. One trap had 3022 SWD in it. In most of the traps the majority of fruit flies in them are SWD — upwards of 95%.

A photomicrograph showing numerous male and female SWD that were caught in a trap.
On the left, males, and on the right, females, counted on June 20, 2020, caught in an SWD trap set in a tart cherry orchard.

Our trap catch data from these berry plantings, confirms findings by other researchers that traps on the crop edge that are near woods catch more SWD than traps set within an insecticide-treated planting. Plantings that are surrounded by open fields, row crops, and roadways tend to have fewer SWD overall, as compared to plantings with wooded edges or ponds, streams and ditches nearby.

As populations of SWD continue to grow across the region, be aware that unprotected, susceptible fruit is at very high risk of SWD infestation, especially if allowed to hang until soft and ripe:

  • blackberry
  • fall raspberry
  • day neutral or ever-bearing strawberry
  • elderberry
  • peach and nectarine
  • plums and prunes

Fruit, such as peaches, nectarines, plums and prunes, that aren't highly susceptible to SWD may escape infestation even without insecticide treatment if harvested before they are fully ripe and soft. All will benefit from cold storage. Keep up on your SWD management tactics. Review the information on the SWD Management page of Cornell Fruit Resources, http://fruit.cornell.edu/spottedwing/management/.

Overall, still a quiet week for SWD trap captures in the Lake Ontario region's tart cherries. Although SWD was caught across the region, only 2 at most in the two traps set per orchard. Traps were checked Monday and Tuesday, June 15 and 16. Elizabeth Tee and Janet van Zoeren, Lake Ontario Fruit Program, and Grace Marshall and Juliet Carroll, NYS IPM Program, are participating in this study along with nine fruit growers.

In our 11 study orchards, SWD has been caught in 5 of the 6 “lake” blocks and in 3 of the 5 “inland” blocks. Specific trap catch results for this week were:

  • Zero SWD in six orchards out of 11.
  • First catch in one orchard = 1 female in edge trap.
  • Recatch in three orchards = 1 male in edge trap; 2 females in edge trap; 1 male & 1 female in interior trap. Each orchard had one week with zero SWD between first catch and this week’s catch.
  • Sustained catch in one orchard = 1 male in interior trap this week and 1 male in edge trap last week.

SWD populations were still low over the past week in tart cherry orchards. What can we credit with keeping SWD populations low, so far? Some possibilities include:

  • Choosing insecticides that are also effective against SWD for other key cherry insect pests such as plum curculio or the Rhagoletis fruit flies (cherry fruit fly, black cherry fruit fly, European cherry fruit fly).
  • The dry weather and low humidity.
  • Lack of alternate fruit resources in the wild, due to freeze events.
  • Slow progression of fruit development, due to the cold spring.
  • Possibly the cold weather last week and cold nights lately.

Populations are low in berries, too, in western NY. This past week, SWD was only caught in one of the 12 berry sites in the Lake Ontario, Finger Lakes, and Central NY regions that we are monitoring.

Cherry fruit is starting to color.

Be watchful of your crop's development. Now is the time to plan your SWD management strategy so you have a good selection of rotational insecticides to protect your crop through to harvest.

Picture of Juliet Carroll, NYS IPM Program, servicing an SWD trap hung in a tart cherry tree.
Juliet Carroll checks a SWD trap in a tart cherry orchard to help determine the need to spray, as fruit ripen.

For cherry fruit fly management (Rhagoletis spp.), choose insecticides that also have activity against SWD to keep the population down and protect your fruit from Rhagoletis fruit flies. Refer to the SWD Insecticide Quick Guide for tree fruit and grapes www.hort.cornell.edu/fruit/pdfs/swd/treefruit-grape-insecticides.pdf. Cross-reference this with the Cornell Pest Management Guidelines for Commercial Tree Fruit Production. Select insecticides wisely. 

SWD can lay eggs in ripening cherries. If SWD has been caught in your orchard, ripening and ripe cherries will be at risk of SWD infestation. Pay close attention to preharvest intervals (PHI) and plan insecticide use so you have materials with lower PHI for use close to harvest. Rotate IRAC groups for resistance management. Drosophilids are known to develop insecticide resistance. Follow label directions. Be wise.

SWD management tactics

  • Mowing – to reduce humidity and niches for SWD harborage and to increase sun penetration. Research has shown this works in tart cherry orchards in Michigan.
  • Weed management – to reduce humidity, alternate fruiting hosts and harborage and to increase sun penetration.
  • Pruning – to reduce humidity and to increase sun and spray penetration. Research has shown this works in tart cherry orchards in Michigan. Improve your pruning strategy this winter.
  • Monitoring – to know if SWD is present when fruit is ripening. Don't spray unless SWD is caught. Some years your crop may not need a targeted program for SWD.
  • Sanitation – to reduce reproduction harborage and overall SWD population. Important in diversified fruit farms.
  • Cold storage – to slow or kill any eggs and larvae in harvested fruit. Not applicable for a processing crop harvested into water tanks. SWD won't survive in water tanks; larvae may float to the surface or fruit may float higher because the infestation changes their buoyancy.

Bookmark online resources

This week, ending 1 June 2020, first catch was obtained in 4 of 11 tart cherry orchards in the Lake Ontario region. Add to that another orchard that had first catch the previous week (no catch there this week) and we're at almost half of the orchards, especially those within a mile of Lake Ontario, with SWD detections. SWD is starting to show up, though not so much in the berry plantings being monitored across New York. The months of June and July are typical first catch months, so stay tuned — to this blog and also to the ripening of your fruit crops.

Photo of a male SWD taken through a dissecting microscope.
This male SWD was caught during the last week of May in a trap set in a tart cherry orchard. Note the shape, size and position of the characteristic spot on each wing.

Janet van Zoeren, Liz Tee, and Grace Marshall are assisting me with this work in tart cherries. Janet and Liz work in the Lake Ontario Fruit Program of CCE. Grace works in the NYS IPM Program of CCE.

If you grow tart cherries or sweet cherries, keep in mind both these tree fruit crops are susceptible to infestation by SWD when its populations build up near your orchard prior to harvest. It has been shown to be good practice to monitor for this insect in cherries. If you find SWD in your orchard as fruit is ripening, you need to protect the crop with insecticide sprays. If you don't find SWD when fruit is ripening, you don't need to spray and can save a bundle of money.

How to thwart the build up of SWD populations in cherries?

Insecticide choices:

  1. Choose plum curculio insecticides that also have activity against SWD.
  2. Choose cherry fruit fly insecticides that also have activity against SWD.

...a pattern is emerging in this suggested approach.

Cultural tactics:

  • mow to keep the orchard floor drier, less humid, and less favorable to SWD.
  • prune to open the canopy to more air circulation, faster drying, better spray penetration: drier, less humid, and less favorable to SWD.

...a pattern is emerging in the proven research.

Get your 2020 Cornell Pest Management Guidelines for Commercial Tree Fruit Production, from here cropandpestguides.cce.cornell.edu/ or from the CCE LOF or ENYCH Program you belong to.

Learn more about SWD on the Cornell Fruit Resources SWD webpages, fruit.cornell.edu/spottedwing/, and on the NYS IPM Invasives & Exotics webpages, nysipm.cornell.edu/agriculture/fruits/invasive-species-exotic-pests/.

Let knowledge be your best weapon.

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