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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/.

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Sustained catch in Monroe County marks the end of 2020 SWD monitoring. Please join me in thanking all who contribute to this effort! In the blueberry planting in Monroe County, Janet van Zoeren, CCE Lake Ontario Fruit Program, caught 11 SWD in the week ending July 28 (2 males and 9 females).

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

New people

These Cornell University scientists participated in SWD monitoring for the first time this year. A special thanks go out to them for braving COVID-19 and keeping themselves and our growers safe — setting traps, changing lures, servicing traps, and identifying SWD. Plus, dealing with gentle reminders to enter data online or send in first trap catch info so that you, our readers, were kept informed via the blogs and distribution map. Thank you SWD first years!

  • Ariel Kirk, Steuben County CCE
  • Barb Neal, Tioga County CCE
  • Grace Marshall, NYS IPM Program
  • Janet van Zoeren, Lake Ontario Fruit Program
  • Liz Alexander, Chemung County CCE
  • Lydia Brown, Hudson Valley Research Laboratory
  • Sarah Tobin, Eastern NY Commercial Horticulture Program

Regular contributors

These Cornell scientists have been the foundation of our monitoring network! This network would not be possible without their support and contributions — suggestions for improvement, ideas for mapping, perspectives on grower needs and steadfast cooperation. Yes, they've done the trapping and dealt with the gentle reminders and they're still with the program. Thank you SWD trappers!

  • Andy Galimberti, Eastern NY Commercial Hort Program
  • Dave Thorp, Livingston County CCE
  • Don Gasiewicz, Wyoming County CCE
  • Elisabeth Hodgdon, Eastern NY Commercial Hort Program
  • Faruque Zaman, Suffolk County CCE
  • Jim O'Connell, Ulster County CCE
  • Liz Tee, Lake Ontario Fruit Program
  • Natasha Field, Eastern NY Commercial Hort Program
  • Peter Jentsch, Hudson Valley Research Laboratory
  • Sharon Bachman, Erie County CCE

Special thanks go to Laura McDermott!

A picture of Laura McDermott, Extension Educator, hosting a field workshop on SWD.
Laura McDermott, Extension Educator, CCE ENYCHP, gives a talk on SWD at a field workshop featuring hummingbirds in raspberries.

Laura McDermott, Eastern NY Commercial Horticulture Program (ENYCHP), has gone above and beyond to support the SWD monitoring network from its inception in 2013 by building a strong collaboration in Eastern NY with a goal of having a trapping location in every county in the ENYCHP. This year, 9 of 17 counties in ENYCHP participated in SWD monitoring. I know Laura would say she couldn't do this without the willing collaboration of her colleagues in the ENYCHP, in Ulster County CCE, and in the Hudson Valley Research Lab. But, we know that without her efforts in bringing us all together, SWD monitoring in Eastern NY wouldn't be as comprehensive as it is. Thank you Laura!

Sustained catch at the final three sites in the SWD monitoring network: two in Orleans County and one in Wayne County. In raspberries in Orleans County, 8 SWD were caught in 2 traps (3 males and 5 females). In blueberries in Orleans and Wayne Counties 4 (3 males and 1 female) were caught in 2 traps and 5 (2 males and 3 females) in 4 traps, respectively. Growers of the berries on these farms have had an active insecticide program in place for SWD. Insecticide treatments had kept numbers low to non-existent on these farms until now.

SWD populations are building up across New York. In some plantings we are monitoring for research, with minimal to no insecticide program, average catch has been over 5 SWD per trap this week in 12 traps — that's 50 to 100 SWD total.

Low levels of fruit infestation have been detected via salt flotation. You can check your fruit routinely with this technique, which may prove very useful in U-pick operations so you can inform your clientele. Guidelines for Checking Fruit for SWD Larvae in the Field.

A picture of summer fruits on display at a farm market.
Delicious summer fruits will be ready for eating now through fall.

For those who are opening your U-pick operations slowly and steadily during the COVID-19 pandemic, here's a resource developed just for you:

For those who want information on SWD to give to clientele:

Effective management of SWD will become more challenging as the summer continues. Keep in mind the key tactics:

  1. Excellent sanitation to reduce SWD populations: clean harvests and get cull fruit out of the planting.
  2. Canopy and water management to make the environment less favorable: air circulation to keep things drier.
  3. Insecticide sprays will kill SWD adults and thereby reduce egg laying: choose materials with excellent efficacy
  4. Regular fruit sampling: see if SWD larvae are in your fruit and at what level.
  5. Cool harvested fruit immediately: Below 37°F cold storage or in-store coolers will slow, stop, or kill development of SWD larvae and eggs.
Photo of a female SWD on a raspberry.
Female SWD on a raspberry.

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophilafruit.cornell.edu/spottedwing/.

Funding for the SWD Monitoring Network provided by:

  • NYS Berry Growers Association
  • NYS IPM Program
  • USDA NIFA Crop Protection and Pest Management Program

One female SWD was caught in a trap set in a blueberry planting in Monroe County. The traps were checked on July 21, 2020. Fruit is ripe and U-pick is open. These traps are being monitored by Janet van Zoeren, Lake Ontario Fruit Program, Cornell Cooperative Extension. This marks the last county in the SWD monitoring network to reach first catch.

SWD distribution map picture showing counties that monitored SWD in 2020.
The 2020 SWD distribution map shows most counties reporting to the network had first catch in June.

The grower at this location has had an active SWD management program, including insecticide protection. The low trap catch numbers at this location likely are associated with an insecticide program being in place in the planting. As the season progresses, SWD will become more numerous and the risk of fruit infestation will become greater. Consider everything you can do to thwart this insect that either will enhance the efficacy of the insecticide management program or will lower the risk of fruit infestation.

Pest Management for SWD includes:

  • Mowing – to reduce humidity and habitat for SWD and to increase sun penetration.
  • Weed management – to reduce humidity, alternate fruiting hosts and habitat and to increase sun penetration.
  • Pruning – to reduce humidity and to increase sun and spray penetration.
  • Monitoring – to know if SWD is present and at what level.
  • Sanitation – to reduce reproduction harborage and overall SWD population.
  • Cold storage – below 37° F, to slow or kill any eggs and larvae in harvested fruit.

Learn more: SWD Management, fruit.cornell.edu/spottedwing/management/ on Cornell Fruit Resources.

Insecticide Quick Guides for NY State are found here (refresh the page to see the latest version):

For berries -

SWD Management in Blueberry

SWD Management in Raspberry and Blackberry

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophila, fruit.cornell.edu/spottedwing/.

Sustained catch, was obtained in seven counties in NY between June 29 and July 14; numbers hit a high of 57 at one location. Read about the five key tactics that contribute to an aggressive SWD management program below. It may be imperative to begin a spray program to protect ripe fruit. SWD build-up has coincided with harvest season and has translated into a challenging year for SWD management. Harvest is underway in raspberries, blueberries, cherries and winding down in June strawberries. 

Sustained catch on June 29

  • Chemung County – 2 males and 3 females in two traps in a blueberry planting.
  • Livingston County – 1 female in two traps in a blueberry planting.
  • Tioga County – 1 male and 2 females in four traps in a blueberry planting.

Sustained catch on July 2

  • Wyoming County – 1 male and 11 females in 6 traps set in two raspberry plantings.

Sustained catch on July 7

  • Herkimer County – 1 female in four traps in a blueberry planting, down from the prior week, possibly due to the hot and dry weather.
  • Steuben County – 5 males in two traps in a blueberry planting.

Sustained catch on July 14

  • Onondaga County – 34 males and 23 females in four traps in a blueberry planting.

If adult SWD are present on your farm, which they probably are by now, manage them aggressively now that harvests are underway.

Aggressive management entails 5 key tactics:

  1.  Excellent sanitation will reduce SWD populations.
Picture showing a field crew harvesting strawberries.
Field crew harvesting strawberries.

Fruit should be harvested frequently and completely to prevent the buildup of ripe and over-ripe fruit. Unmarketable fruit should be removed from the field and either frozen, “baked” in clear plastic bags placed in the sun, or disposed of in bags off-site. This will kill larvae, remove them from your crop, and prevent them from emerging as adults.

  1. Canopy and water management will make the environment less favorable.

Prune to maintain an open canopy, increase sunlight and reduce humidity. This will make plantings less attractive to SWD and will improve spray coverage. Repair leaking drip lines and avoid overhead irrigation when possible. Allow the ground and mulch surface to dry before irrigating.

  1. Insecticide sprays will kill SWD adults and thereby reduce egg laying:
A photo of a grower learning about sprayer technology at a workshop on SWD.
Learning about spray technology at the Albany workshop.

Insecticide treatments should begin when either regional monitoring alerts about the first SWD trap catch or when highly susceptible fruit crops begin to ripen. Treatments should be applied at least every seven days and repeated in the event of rain. Choose the most effective insecticides with pre harvest intervals that work for your picking schedule. Rotate insecticides according to their modes of action.

Quick reference guides:

Check the Cornell Guidelines (cropandpestguides.cce.cornell.edu/) for the latest list of approved pesticides. Special needs labels are being sought for NY berries. Always read and follow the pesticide label instructions.

  1. Regular fruit sampling:
A grower checks a blueberry fruit sample for SWD larvae using salt flotation.
Checking fruit for larva with salt flotation at the Albany workshop.

At least 100 fruit per block per harvest should be observed for infestation. Talk to your local CCE agent about a monitoring program. Fruit can be inspected for evidence of larval feeding. Small holes in berries where the eggs were laid may leak juice when the berry is gently squeezed; this is especially diagnostic on blueberry. Infested red raspberry fruit may leave a red juice stain on the berry receptacle when the fruit is picked. Fruit with small indents or bruises where the berry surface appears to have flattened or deflated may be damaged.

A salt flotation method, immersing fruit in a solution of 1 Tbsp. (14.8 cc) table salt per 1 cup (236.6 ml) water, may cause larvae to float to surface. At least 100 fruit per block per harvest should be observed for infestation. Suggested methods were adapted for NY growers in Guidelines for Checking Fruit for SWD Larvae in the Field (cpb-us-e1.wpmucdn.com/blogs.cornell.edu/dist/0/7265/files/2017/01/SaltFloatation-2kmt284.pdf).

  1. Cool berries immediately:

Chilling berries immediately after harvest to 32° – 33° F will stop the development of larvae and eggs in the fruit, and may kill them. U-Pick customers should be encouraged to refrigerate fruit immediately to maintain fruit quality at home. Below 37° F SWD stops developing in fruit.

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophila, fruit.cornell.edu/spottedwing/.

Thanks go out to:

  • Liz Alexander, Chemung County CCE, who is monitoring the site in Chemung County
  • Dave Thorp, Livingston County CCE, who is monitoring the site in Livingston County
  • Barb Neal, Tioga County CCE, who is monitoring the site in Tioga County
  • Don Gasiewicz, Wyoming County CCE, who is monitoring sites in Wyoming County
  • Andy Wereszczack, blueberry grower, and Juliet Carroll, NYSIPM CCE, who are monitoring the site in Herkimer County.
  • Ariel Kirk, Steuben County CCE, who is monitoring the site in Steuben County
  • Grace Marshall, NYSIPM CCE, who is monitoring the site in Onondaga County

In a blueberry planting in Herkimer County six SWD were caught in four traps during the week ending June 30, 2020. No zero catch was obtained at this site. Traps were initially set on June 23. These traps are being monitored by the grower at this location.

Photo of a male SWD on a blueberry.
A male spotted wing drosophila (SWD) on blueberry; another likely SWD is in the background.

Across New York there is only one location in the SWD Monitoring Network where SWD hasn't been caught yet, in Western, NY. Weather in Western NY has been hot. Temperatures have reached or exceeded 90° F during the past several days. Lack of rain has occurred in many areas.

Over 90° F weather doesn’t favor SWD survival. This was determined in lab assays following 24-hr-long exposure to high temperature treatments and assessing the lethal temperature for 25%, 50% and 75% of the treated SWD. I wrote a blog about this research in 2014, might be worth a look, Frozen or baked SWD?, at blogs.cornell.edu/swd1/2014/04/08/frozen-or-baked-swd/.

I would hazard a guess that the lethal effects of high temperature and an insecticide are enhanced one by the other, possibly synergistically – though this would require further research.

Mowing row middles makes a lot of sense right now – eliminate cool, shady refuges for SWD; reduce competition for water from groundcover.

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophila, fruit.cornell.edu/spottedwing/.

In a blueberry planting in Steuben County, we now have first catch. A single male was found in a trap set on the edge of the planting that was checked on July 1, 2020 by Ariel Kirk, Agriculture Educator, Steuben County Cornell Cooperative Extension. A big shout out to Ariel. This is her first year with the network.

In many areas of New York State, blueberries are ripe, but in others, they are still green. Make sure you tailor your SWD Management accordingly, because green and hard fruit aren't susceptible to SWD.

This picture shows a treefrog sitting on the lid of a trap for SWD.
A convenient place for a treefrog to sit to capture a free meal of fruit flies attracted to the SWD trap. It even went along for the ride when the trap was checked!

Some help from a treefrog? Or is the treefrog enjoying easy pickings? I think this is the common gray treefrog (Hyla versicolor). No matter, these insectivores help reduce the number of insects in our fields. This toad helped Grace Marshall, NYS IPM, check an SWD trap this spring when blueberries were in full bloom.

Sustained catch, was obtained in 11 berry plantings in nine counties in NY between June 23 and 29. Trap catch numbers are creeping up and are hitting higher numbers some locations. Harvest continues in June strawberries and is now underway in raspberries (yum, my personal favorite) and blueberries.

With SWD found across most traps in NY and numbers climbing, it will be imperative to begin a spray program to protect fruit. SWD populations built up this year to coincide with berry and cherry harvests. This translates into a challenging year for SWD management.

Sustained catch on June 23

  • Clinton County – 1 male and 1 female in a blueberry planting.
  • Essex County - 6 males and 16 females in a raspberry planting.
  • Orange County - 35 males and 21 females in a raspberry field.

Sustained catch on June 25

  • Saratoga County – 4 males and 10 females in a blackberry planting.
  • Saratoga County – 3 males and 5 females in a tart cherry orchard.
  • Schuyler County - 1 male and 2 females in a blueberry planting.
  • Schuyler County - 1 male and 9 females in a raspberry planting.
  • Cayuga County - 1 males and 2 females in a raspberry planting.

Sustained catch on June 29

  • Columbia County - 2 males and 4 females in a tart cherry orchard.
  • Washington County - 1 male and 7 females in a blueberry planting.
  • Wayne County - 1 female in a raspberry planting.
This map shows the counties in the SWD monitoring network where SWD has been found. Mostly in June in 2020.
The distribution map shows that SWD has been found in all trap locations except those in Monroe and Steuben County. First catch occurred mainly in June in 2020.

SWD has now been found in traps set in all but two counties in the monitoring network, but that doesn't mean it's not present in those counties. It is time to take SWD management seriously. If adult SWD are present on your farm, manage them aggressively now that harvests are underway and imminent.

Aggressive SWD management entails 5 key tactics:

  1. Excellent sanitation will reduce SWD populations.

Fruit should be harvested frequently and completely to prevent the buildup of ripe and over-ripe fruit. Unmarketable fruit should be removed from the field and either frozen, “baked” in clear plastic bags placed in the sun, or disposed of in bags off-site. This will kill larvae, remove them from your crop, and prevent them from emerging as adults.

  1. Canopy and water management will make the environment less favorable.

Prune to maintain an open canopy, increase sunlight and reduce humidity. This will make plantings less attractive to SWD and will improve spray coverage. Repair leaking drip lines and avoid overhead irrigation when possible. Allow the ground and mulch surface to dry before irrigating.

  1. Insecticide sprays will kill SWD adults and thereby reduce egg laying:

Insecticide treatments should begin when either regional monitoring alerts about the first SWD trap catch or when highly susceptible fruit crops begin to ripen. Treatments should be applied at least every seven days and repeated in the event of rain. Choose the most effective insecticides with pre harvest intervals that work for your picking schedule.

Rotate insecticides according to their modes of action.

Quick reference guides:

Check the Cornell Guidelines (cropandpestguides.cce.cornell.edu/) for the latest list of approved pesticides. Special needs labels are being sought for NY berries. Always read and follow the pesticide label instructions.

  1. Regular fruit sampling:

At least 100 fruit per block per harvest should be observed for infestation. Talk to your local CCE agent about a monitoring program. Fruit can be inspected for evidence of larval feeding. Small holes in berries where the eggs were laid may leak juice when the berry is gently squeezed; this is especially diagnostic on blueberry. Infested red raspberry fruit may leave a red juice stain on the berry receptacle when the fruit is picked. Fruit with small indents or bruises where the berry surface appears to have flattened or deflated may be damaged.

A salt flotation method, immersing fruit in a solution of 1 Tbsp. (14.8 cc) table salt per 1 cup (236.6 ml) water, may cause larvae to float to surface. At least 100 fruit per block per harvest should be observed for infestation. Suggested methods were adapted for NY growers in Guidelines for Checking Fruit for SWD Larvae in the Field (https://cpb-us-e1.wpmucdn.com/blogs.cornell.edu/dist/0/7265/files/2017/01/SaltFloatation-2kmt284.pdf).

  1. Cool berries immediately:Chilling berries immediately after harvest to 32o – 33o F will slow or stop the development of larvae and eggs in the fruit. U-Pick customers should be encouraged to refrigerate fruit immediately to maintain fruit quality at home.

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophila, http://fruit.cornell.edu/spottedwing/.

Thanks go out to:

  • Elisabeth Hodgdon, ENYCHP CCE, who is monitoring Clinton County
  • Andy Galimberti, ENYCHP CCE, who is monitoring Essex County
  • Natasha Field, ENYCHP CCE, who is monitoring Saratoga and Columbia Counties
  • Grace Marshall, NYSIPM CCE, who is monitoring Cayuga, Schuyler and Wayne Counties
  • Sarah Tobin, ENYCHP CCE, who is monitoring Orange County
  • Laura McDermott, ENYCHP CCE, who is monitoring Washington County

Sustained catch of a single male SWD in a trap set in a blueberry planting was found in Erie County. The traps were checked on June 24, 2020. Interestingly, the prior week when first catch was obtained on June 17 there were more SWD caught — one male and two females.

This can sometimes happen if weather conditions are unfavorable, extreme heat and dry conditions, or could result from insecticide applications that were made to manage SWD or other insects. These traps are being monitored by Sharon Bachman, Erie County Cornell Cooperative Extension.

So far, SWD has been caught in 21 of the 23 counties where traps are being monitored across NY State. Sustained catch – two weeks in a row – has occurred in about 11 of those counties.

Fruit is ripening across western NY and becoming susceptible to egg-laying. Brush up on SWD management, http://fruit.cornell.edu/spottedwing/management/ on Cornell Fruit Resources.

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophila, http://fruit.cornell.edu/spottedwing/.

One female SWD was caught in a trap set in a blueberry planting in Wyoming County. The traps were checked on June 25, 2020. The crop is developing nicely. It is essential to keep close watch on the stage of ripeness, to know when fruit becomes susceptible to egg-laying — at pink to purple color. These traps are being monitored by Don Gasiewicz, Wyoming County Cornell Cooperative Extension.

Picture of strawberry fruit with an egg-laying site.
Evidence of oviposition into June strawberry found today, 20 June 2019, by Jim O'Connell, CCE Assoc of Ulster County. Notice the delicate white breathing tubes and the small area of sunken, tan tissue where the larva is inside the fruit.

This blueberry planting is immediately adjacent to a large strawberry planting. We know from prior years and reports from other states that when June strawberry harvests are done, the number of SWD caught in traps often spikes. Whether this is coincidence or related to something specific with June strawberries serving as a resource for SWD, we aren’t quite sure. But, suffice it to say, that if you have June strawberries and are also growing blueberries or raspberries or cherries nearby, renovate the June strawberry fields ASAP. Please review methods for doing this effectively on the post by Laura McDermott, Renovate June Strawberry Fields Promptly, https://blogs.cornell.edu/swd1/2018/06/27/renovate-strawberry-plantings-promptly/

SWD Resources

SWD Management, http://fruit.cornell.edu/spottedwing/management/ on Cornell Fruit Resources.

Insecticide Quick Guides for NY State are found here (refresh the page to see the latest version):

SWD Management in Blueberry

SWD Management in Raspberry and Blackberry

Check out the information on Cornell Fruit Resources Spotted Wing Drosophila, fruit.cornell.edu/spottedwing/.

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