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Fruit that has dropped to the ground in orchards and berry plantings provides resources for SWD — food and reproduction. Populations of SWD are climbing. SWD made up almost half of the fruit flies caught in traps in an unsprayed research site where ~300 were caught in four traps.  I've seen lots of fruit flies (of various species, including the distinctive male SWD) flitting around the dropped apples in my yard that have been chewed on and pecked at by chipmunks, squirrels, and my chickens (this particular apple tree has been defoliated by apple scab this year and won't carry the crop.)

Picture showing an SWD larva in a pokeweed berry.
SWD larva in a pokeweed berry. Pokeweed is a very suitable host for SWD reproduction.

WEEDS! Pokeweed fruit are starting to ripen; SWD thrives in those fruit.

We've got a long way to go before the SWD season is over. This is the time of year that management has to be consistent and constant:

  • maintain an appropriate insecticide program
  • routinely sample fruit with salt flotation to check for larvae
  • keep weeds down
  • prevent leaks in irrigation systems (gosh, it's like a water paradise for SWD!)
  • keep plants well pruned and staked
  • remove cull fruit from the planting or drop it to the ground

And, while I'm on the subject of cull fruit, I've revised the SWD insecticide guide for treating dropped fruit on the ground. Here's the link to the Quick Guide to SWD insecticides for treating dropped fruit, www.hort.cornell.edu/fruit/pdfs/swd/drop-cull-insecticides.pdf . Make sure to refresh your browser so you don't pull up last year's — the new one should say August 2019 on it.

Keep on top of SWD Management, review the SWD Management pages on Cornell Fruit Resources, fruit.cornell.edu/spottedwing/management/.

Blueberries are highly susceptible to SWD. Although early maturing varieties can escape infestation in some years, that hasn’t been the case this year in many areas of NY State. U-Pick and farm stand customers want the best from farm-fresh blueberries and SWD can mar that experience — so be proactive — make sure your customers know what you’re up against. Wholesale and processing blueberry growers know there’s zero tolerance for SWD in fruit at the retailer and processor. It’s time to learn how to protect this crop to protect your markets!

A picture showing two male SWD on a blueberry.
Two male SWD on a blueberry, photographed in early September 2013. SWD populations typically build to very high levels in late summer and early autumn.

The female SWD fruit flies can lay eggs in ripe blueberries, but also in ones that are ripening, even only pink. And because SWD has been caught at all monitoring locations across NY State, it is fair to say that the blueberry harvests currently underway are highly vulnerable to infestation.

An insecticide program is an essential component of managing SWD in blueberries; this year it will be in early-, mid-, and late-season varieties.

Things to consider regarding insecticide programs for SWD, with specific emphasis on materials registered for blueberries:

  • Population growth models for SWD calculate, theoretically, that using the most efficacious insecticide first will more successfully lower SWD numbers by knocking the population back to close to zero and delaying population growth. (This is strikingly similar to classic principles of plant disease epidemiology and tactics in plant disease management.)
  • Rotate use among insecticides with different IRAC groups -- related to the mode of action of the insecticide -- to reduce selection pressure for insecticide-resistant populations of SWD. (IRAC codes are usually given on the first page of the pesticide label near the product name. For example, Group 3A Insecticide.
  • Insecticides with probable excellent efficacy include – Delegate WG (3 days), Delegate WG supplemental label (1 day), Exirel (3 days), Bifenture 10DF (1 day), Brigade WSB 2(ee) (1 day), Danitol 2.4EC (3 days), and Mustang Maxx (1 day), Lannate SP (3 days), Lannate VP (3 days), and Imidan (3 days). Of these, choose first the one with the longest pre-harvest interval (given in parentheses) that you can accommodate; some may be out of the question at this point. Rotate to other insecticides with shorter pre-harvest intervals for closer to harvest.
  • After using a highly efficacious insecticide, for the subsequent application, it is usually adequate to use an insecticide that has lower efficacy – Entrust Naturalyte 2(ee) (3 day3), Entrust SC 2(ee) (1 day), Assail 30SG 2(ee) (1 day), Malathion 5EC 2(ee) (1 day), Malathion 8 Aquamul 2(ee) (1 day), or Malathion 57 2(ee) (1 day).
  • For organic production, Entrust Naturalyte 2(ee) (3 days) and Entrust SC 2(ee) (1 day) are the most efficacious organically-approved insecticides. Rotate this active ingredient with either Pyganic (0 days), AzaSol (0 days), Grandevo (0 days), or Venerate (0 days) along with shortening the number of days between the spray intervals.
  • The spray interval column in the Insecticide Quick Reference Guide table relates to use of the same product back-to-back. When switching to another mode of action, more frequent applications are OK and are suggested against SWD.
  • Rainfast? Research on berries has shown Mustang Maxx isn’t very rain fast, so plan to re-cover if significant rain occurs during the spray interval. This is good practice with SWD or any insecticide program if the rainfall meets or exceeds an inch of rain.
  • Don’t stretch intervals between sprays more than seven days.
  • Get excellent coverage. Spray every row (no alternate row spraying.)

Review the Quick Reference Guide to SWD Insecticides for berries at
www.hort.cornell.edu/fruit/pdfs/swd/berry-insecticides.pdf

Other tactics that can help considerably are:

Re-set blueberry fields: Because blueberries don’t all ripen at the same rate in the fruit cluster, it is possible and advisable to “re-set” the field. When fruit infestation is found via salt flotation or high numbers of SWD are caught in traps in the field, clean pick all ripe and cull fruit. Remove cull fruit from the planting and solarize it or freeze it to kill SWD. Solarize in sealed, clear plastic bags set in the sun. After clean picking, spray insecticide. Choose a material with excellent efficacy against SWD and an appropriate days-to-harvest interval.

Sanitation: Pick off and remove all cull fruit from the planting. Routine sanitation can be very beneficial in IPM – it eliminates SWD food and egg-laying resources and slows population growth. And when done routinely, it takes a lot less time and is a lot more effective. Cull fruit can be placed in clear plastic bags and left in the sun to bake or placed in a freezer to kill SWD eggs and larvae.

Mowing: Keeps the environment in the plant’s microclimate hot, sunny, and dry. On diversified farms, do be careful when timing mowing or renovation of strawberry fields so as to reduce movement of SWD from that crop into the next ripening crop on your farm. See last year’s blog on strawberry renovation, blogs.cornell.edu/swd1/2018/06/27/renovate-strawberry-plantings-promptly/.

Weed management: Keeps the environment in the plant’s microclimate hot, sunny and dry, and provides no alternate hosts. Be mindful of crops no longer being harvested. Cull fruit, unprotected with insecticide, left in those fields will provide resources for SWD population growth.

Pruning: Keeps the environment in the plant’s microclimate hot, sunny and dry, and improves spray penetration and deposition. Prune blueberries yearly. Prune shoots at the base of the plant, don’t prune out portions of shoots. Leave the best two shoots in each age category when pruning established plantings. This keep the plant balanced, growing vigorously, and fruiting well.

Cold storage: Put harvested fruit into a cooler at 32-34 F as soon as possible after harvest. Hold it there to slow and kill SWD larvae and eggs. Blueberries can tolerate 32 F storage conditions.

Consult Cornell Fruit Resources SWD Management, fruit.cornell.edu/spottedwing/management/.

Monitoring tips for SWD

Salt flotation: Routinely sample a subset of fruit that’s being harvested using salt flotation to alert you to the presence of larvae in fruit. A simple method for this is in Guidelines for Checking Fruit for SWD Larvae in the Field by Laura McDermott, Download it from the Cornell Fruit Resources SWD Monitoring page, fruit.cornell.edu/spottedwing/monitoring/.

Two growers describe their success using salt flotation to monitor infestations in blueberries, detailed on the blog, Use salt flotation to check for SWD, blogs.cornell.edu/swd1/2018/09/11/use-salt-flotation-to-check-for-swd/

Picture of three SWD males.
Three male spotted wing Drosophila. Note the spot on each wing, which is on the end of the first vein from the outer edge of the wing.

Traps: It is relatively easy to use red or yellow sticky cards to monitor for the distinctive male SWD in fruit plantings. Set the sticky card traps on the edge of the planting where it is convenient to read them daily. Use a coffee stirrer to scrape off and discard the stuck insects daily and replace the sticky card when its stickiness has worn off. Here’s one place you can order trap and lure supplies – Great Lakes IPM, www.greatlakesipm.com/.

SWD populations will build rapidly when fruit is available for oviposition sites, during warm, humid, cloudy weather, and wherever crop canopies are dense and weeds are not managed or mowed. A mated female can lay about 1-3 (or more) eggs per fruit, 7-16 eggs per day, and about 350 eggs during her life span of about three weeks.

So stay informed!

Comprehensive information on SWD IPM is available in Spotted Wing Drosophila IPM in Blueberries from the NE IPM Center SWD Working Group, neipmc.org/go/swdpub2

Consult Cornell Fruit Resources SWD Management, fruit.cornell.edu/spottedwing/management/.

Refer to the Cornell Pest Management Guidelines, cropandpestguides.cce.cornell.edu/ and always have the latest version -- the 2019 version for Berry Crops.

For organic growers, Management Recommendations for Spotted Wing Drosophila in Organic Berry Crops, www.canr.msu.edu/ipm/uploads/files/SWD/SWDOrganicBerryCrops.PDF

SWD prefers nice ripe fruit — like we do! And blueberries are sooo delicious!

The ability for the SWD population to explode as summer rolls on was demonstrated last week in several counties where I have research projects. Per trap, 5 to 125 SWD were caught in raspberry, blueberry, and tart cherry in mid-July. The totals for the two to four traps set in the orchards and fields were 14 to 250.

Use this summary as a wake up call! For the weeks ending on the date given:
7/11/2019, Schuyler County, blueberry, 4 traps, 22 SWD (11 males and 11 females)
7/11/2019, Schuyler County, raspberry, 4 traps, 108 SWD (64 males and 44 females)
7/22/2019, Herkimer County, blueberry, 4 traps, 30 SWD (12 males and 18 females)
7/22/2019, Wayne County, tart cherry, 2 traps, 14 SWD (1 male and 13 females)
7/22/2019, Wayne County, tart cherry, 2 traps, 24 SWD (4 males and 20 females)
7/22/2019, Wayne County, tart cherry, 2 traps, 57 SWD (9 males and 48 females)
7/22/2019, Wayne County, tart cherry, 2 traps, 85 SWD (19 males and 66 females)
7/22/2019, Wayne County, tart cherry, 2 traps, 250 SWD (60 males and 190 females)
7/23/2019, Wayne County, blueberry, 2 traps, 131 SWD (53 male and 78 females)
7/23/2019, Wayne County, blueberry, 4 traps, 29 SWD (14 male and 15 females)

In eight of the nine sites a spray program was in place to protect fruit. Fruit is ripe and being harvested – and it’s delicious! Fruit isn’t showing signs of infestation, which means insecticide programs can protect fruit from oviposition, even when SWD numbers are high. Download the Quick Reference Guide to SWD Insecticides at

Photo of the three instars of SWD.
The three instars of SWD will emerge from fruit immersed in a salt solution. The smallest instar is about 0.5 mm long, the largest about 2 mm long.

Salt flotation – What  these numbers also demonstrate is that trap catch numbers aren’t necessarily an indication of whether or not an insecticide program is working. A better indication is to sample fruit and run a salt flotation test. Two berry growers described their success last year using salt flotation to monitor infestations in blueberries, detailed on the blog, Use salt flotation to check for SWD.  A simple method is described in Guidelines for Checking Fruit for SWD Larvae in the Field by Laura McDermott, which can be downloaded from Cornell Fruit Resources SWD Monitoring pages, fruit.cornell.edu/spottedwing/monitoring/. Large scale berry growers will routinely run salt flotation at each harvest, because blueberries, raspberries, and blackberries ripen and are harvested over several weeks. For crops that are harvested all at once, like tart cherry, salt flotation may not be as useful.

Refrigeration – The high populations of SWD, coupled with later ripening of many crops this year, make it even more important to immediately cool fruit after harvest. Cold storage temperatures close to 32°F can greatly inhibit and even kill SWD in fruit. Raspberries, blackberries, blueberries, and tart cherries will all tolerate cold storage temperatures between 32°F to 34°F.

Diversified fruit farms – Protect your crops from SWD, if you’re growing susceptible fruit – June strawberries, day-neutral strawberries, sweet cherries, tart cherries, raspberries, blackberries, elderberries, blueberries, peaches, nectarines, plums, prunes, and thin-skinned grapes. If you have a diversified fruit farm, SWD can spill over from one crop to the next as they are harvested and especially when cull fruit remains in the field. Renovate strawberry fields promptly.

Photograph of high tunnel raspberries.
High tunnel raspberries.

Fruit becomes susceptible to SWD oviposition when it is ripening and is highly susceptible when it is ripe – raspberry, blackberry, blueberry, sweet cherry, tart cherry, elderberry. Fruit that is less susceptible will be attacked when it is at peak ripeness – peach, nectarine, plum, prune, strawberry, grapes. All fruit can serve as a resource for feeding and breeding when it is left for cull in the field. The good news is that, in degraded fruit, SWD doesn't compete all that well with other Drosophilas, like Drosophila melanogaster, our common vinegar fly, which often shows up in our kitchens in late summer or in the winery during press. SWD prefers nice ripe fruit — like we do!

Raspberries are just about the most susceptible fruit crop grown in New York State. It’s time to learn how to protect this crop! Fruit that is ripening and ripe is at risk of infestation. SWD has been caught at all but one of the monitoring locations across the State and raspberry harvests are underway.

Picture showing SWD on a raspberry.
Meet and greet - male (right) and female (left) SWD - on a raspberry fruit.

This year summer raspberry (floricane types) won’t escape infestation simply because their fruiting season is earlier than fall raspberry (primocane types). Both types of raspberries will be highly vulnerable.

An insecticide program is an essential component of managing SWD in fall raspberries; this year it will be in summer raspberries, as well. Things to consider regarding insecticide programs for SWD, with specific emphasis on materials registered for raspberries:

  • Population growth models for SWD calculate, theoretically, that using the most efficacious insecticide first will more successfully lower SWD numbers by knocking the population back to close to zero and delaying population growth. (This is strikingly similar to classic principles of plant disease epidemiology and tactics in plant disease management.)
  • Rotate use among insecticides with different IRAC groups — related to the mode of action of the insecticide — to reduce selection pressure for insecticide-resistant populations of SWD.
  • Insecticides with probable excellent efficacy include – Delegate WG (1 day), Bifenture 10DF (3 days), Brigade WSB 2(ee) (3 days), Brigade EC 2(ee) (3 days), Danitol 2.4EC (3 days), and Mustang Maxx (1 day). Of these, choose first the one with the longest pre-harvest interval (given in parentheses) that you can accommodate; some may be out of the question at this point. Rotate to other insecticides with shorter pre-harvest intervals for closer to harvest.
  • After using a highly efficacious insecticide, for the subsequent application, it is usually adequate to use an insecticide that has lower efficacy – Entrust Naturalyte 2(ee) (1 day), Entrust SC 2(ee) (1 day), Assail 30SG 2(ee) (1 day), Malathion 5EC 2(ee) (1 day), Malathion 8 Aquamul 2(ee) (1 day), Malathion 57 2(ee) (1 day), or Molt-X (0 days).
  • For organic production, Entrust 2(ee) (1 day) (Naturalyte and SC formulations) is the most efficacious organically-approved insecticide. Rotate this material with either Pyganic (0 days), AzaSol (0 days), Grandevo (0 days), or Venerate (0 days).
  • The spray interval column in the Insecticide Quick Reference Guide table relates to use of the same product back-to-back. When switching to another mode of action, weekly applications are OK and are suggested against SWD.
  • Research on berries has shown Mustang Maxx isn’t very rain fast, so plan to re-cover if significant rain occurs during the spray interval.
  • Don’t stretch intervals between sprays more than about seven days.
  • Get excellent coverage. Spray every row (no alternate row spraying.)

Review the Quick Reference Guide to SWD Insecticides for berries at www.hort.cornell.edu/fruit/pdfs/swd/berry-insecticides.pdf

Other tactics that can help considerably are:

Picture of a male SWD on a blackberry.
Male SWD on blackberry in August.

Re-set raspberry and blackberry fields: Because raspberry and blackberry continue to flower and set fruit over a protracted period of time, it is possible and advisable to “re-set” the field. When fruit infestation is found via salt flotation or high numbers of SWD are caught in traps in the field, clean pick all ripe and cull fruit. Remove this fruit from the planting and solarize it or freeze it to kill SWD. Solarize in sealed, clear plastic bags set in the sun. After clean picking, spray insecticide. Choose a material with excellent efficacy against SWD and an appropriate days-to-harvest interval.

Sanitation: Pick off and remove all cull fruit from the planting. Routine sanitation can be very beneficial in IPM — it eliminates SWD food and egg-laying resources and slows population growth. And when done routinely, it takes a lot less time and is a lot more effective. Cull fruit can be placed in clear plastic bags and left in the sun to bake or placed in a freezer to kill SWD larvae.

Mowing: Keeps the environment in the plant’s microclimate hot, sunny, and dry. On diversified farms, do be careful when timing mowing or renovation of strawberry fields so as to reduce movement of SWD from that crop into the next ripening crop on your farm. See last year’s blog, Renovate strawberry plantings promptly, blogs.cornell.edu/swd1/2018/06/27/renovate-strawberry-plantings-promptly/.

Weed management: Keeps the environment in the plant’s microclimate hot, sunny and dry, and provides no alternate hosts.

Pruning: Keeps the environment in the plant’s microclimate hot, sunny and dry, and improves spray penetration and deposition. Find out details about how this can be done in raspberry on this blog, Pruning caneberries to minimize SWD habitat within the planting, blogs.cornell.edu/swd1/2017/06/27/pruning-caneberries-to-minimize-swd-habitat-within-the-planting/

Cold storage: Put harvested fruit into a cooler at 32-34 F as soon as possible after harvest. Hold it there to slow and kill SWD larvae and eggs. Raspberries can tolerate 32 F storage conditions.

Consult Cornell Fruit Resources SWD Management, fruit.cornell.edu/spottedwing/management/.

Monitoring tips for SWD

Salt flotation: Routinely sample a subset of fruit that’s being harvested using salt flotation to alert you to the presence of larvae in fruit. A simple method for this is in Guidelines for Checking Fruit for SWD Larvae in the Field by Laura McDermott, available on Cornell Fruit Resources SWD pages at cpb-us-e1.wpmucdn.com/blogs.cornell.edu/dist/0/7265/files/2017/01/SaltFloatation-2kmt284.pdf.

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

Two growers describe their success using salt flotation to monitor infestations in blueberries, detailed on the blog, Use salt flotation to check for SWD, blogs.cornell.edu/swd1/2018/09/11/use-salt-flotation-to-check-for-swd/

Traps: It is relatively easy to use red or yellow sticky cards to monitor for distinctive male SWD's in fruit plantings. Set the sticky card traps on the edge of the planting where it is convenient to read them daily. Use a coffee stirrer to scrape off and discard the stuck insects daily and replace the sticky card when its stickiness has worn off. Here’s one place you can order trap and lure supplies – Great Lakes IPM, www.greatlakesipm.com/.

SWD populations will build rapidly when fruit is available for oviposition sites, during warm, humid, cloudy weather, and wherever crop canopies are dense and weeds are not managed or mowed. A mated female can lay about 1-3 (or more) eggs per fruit, 7-16 eggs per day, and about 350 eggs during her life span of about three weeks.

So stay informed!

Comprehensive information on SWD IPM is available in Spotted Wing Drosophila IPM in Raspberries & Blackberries from the NE IPM Center SWD Working Group, neipmc.org/go/swdpub1

Consult Cornell Fruit Resources SWD Management, fruit.cornell.edu/spottedwing/management/.

Refer to the Cornell Pest Management Guidelines, cropandpestguides.cce.cornell.edu/ and always have the latest version -- the 2019 version for Berry Crops.

For organic growers, Management Recommendations for Spotted Wing Drosophila in Organic Berry Crops, www.canr.msu.edu/ipm/uploads/files/SWD/SWDOrganicBerryCrops.PDF

SWD prefers nice ripe fruit — like we do! Let’s keep our fruit to ourselves!

IPM guides for SWD in brambles and blueberries are now available — just in time for the 2019 growing season! The early arrival of SWD in New York will surely motivate you to review the information in these IPM guides. Download them from the Northeastern IPM Center website, provided below, or via the SWD IPM Working Group website, www.northeastipm.org/working-groups/spotted-wing-drosophila/. Feature them in your newsletters, share them with extension educators, consultants and growers.

Spotted Wing Drosophila IPM in Raspberries & Blackberries
neipmc.org/go/swdpub1

Spotted Wing Drosophila IPM in Blueberries
neipmc.org/go/swdpub2

Photo of a female SWD on a raspberry.
Female SWD on a raspberry.

Authors of the raspberry & blackberry IPM guide -
Greg Loeb, Entomology, Cornell Univ
Juliet Carroll, IPM, Cornell Univ
Nicole Mattoon, IPM, Cornell Univ
Cesar Rodriguez-Saona, Entomology, Rutgers
Dean Polk, Agric & Resource Mngmt, Rutgers
Laura McDermott, ENYCHP, Cornell Univ
Anne Nielsen, Entomology, Rutgers

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

Authors of the blueberry IPM guide -
Cesar Rodriguez-Saona, Entomology, Rutgers
Juliet Carroll, IPM, Cornell Univ
Nicole Mattoon, IPM, Cornell Univ
Dean Polk, Agric & Resource Mngmt, Rutgers
Greg Loeb, Entomology, Cornell Univ
Laura McDermott, ENYCHP, Cornell Univ
Anne Nielsen, Entomology, Rutgers

Input to the SWD IPM guides was also provided by the Northeast IPM SWD Working Group.

Research in raspberries at Cornell AgriTech over the last four years has shown promise as an alternative tactic to reduce the impact of SWD on berries. As described in a previous blog posted in 2014, Hummingbirds, these birds may indeed enjoy eating SWD.

A trend of fewer SWD caught in traps in positions 1-4, where hummingbird feeders are located, compared to more being caught in positions 5-9, where there are no hummingbird feeders, in a transect along a raspberry planting.

Preliminary data analysis for 2018 shows that when SWD numbers are very low or very high, there is little to no difference in the number of SWD caught in Scentry traps placed in the area of the field with hummingbird feeders compared to those in the area of the field without feeders. However, when numbers are moderate, there was a difference. Along a transect down the length of the field, the trend was for there to be fewer SWD in the hummingbird feeder area compared to the no-feeder area, as shown in the chart.

The diet of an average hummingbird consists mostly of flower nectar and insects. Flower nectar provides sugar to support their high metabolic rate… even higher during flight due to their rapid wing flapping rates. The insects hummingbirds eat provide them with protein, amino acids, and necessary vitamins and minerals. The insects must be small enough to swallow whole during flight — watch out, SWD!

A grower at the SWD workshop watches as a hummingbird visits a feeder in the raspberry planting.

Two grower demonstrations were undertaken this year, as well. One in blueberry and one in raspberry. Both growers undertook cleaning the feeders and changing the sugar solution twice per week to keep the hummingbirds well fed and active within their plantings. At the workshop held in Salem, NY last month, several of the tiny birds were seen dashing about.

Placing and maintaining 25 hummingbird feeders per acre, may be a bit too arduous for some growers. This is the number of feeders we've been using in our research and grower demonstration plots and the number used by the blackberry grower in Mississippi.

Female or young ruby-throated hummingbird on a feeder set above a blueberry planting. Photo: R. Parker

Other ways to attract hummingbirds to your berry planting that don't rely on the use of feeders, would involve allocating space for flowering plants that they prefer. Interplanting with rows of Monarda (bee balm), for instance, would be one approach.

Of course, SWD is around a lot longer than hummingbirds, which have, at this point in time, likely flown off to the South on their journey to the Yucatan peninsula in Central America. Flying across the Gulf of Mexico or along Mexico's coast, they make their way to their overwintering grounds. And, as SWD populations explode in late summer, it is difficult to control SWD, let alone rely on a flying predator.

A humming"baby" feeder?

If you think hummingbirds don't eat small insects, then guess again! I've seen these contraptions showing up in stores this year — to feed hummingbirds. They are rearing capsules for fruit flies (vinegar flies, as entomologists call them). Perhaps someone should tell them we don't need more SWD? ...just more hummingbirds!

 

The three instars of SWD will emerge from fruit immersed in a salt solution. The smallest instar is about 0.5 mm long, the largest about 2 mm long.

Effective use of salt flotation will help you determine if your fruit are infested with SWD and if your spray program is working. It also will give you a perspective on what your customers may find when they take the fruit home to eat fresh or to make pies, jellies, jams and preserves.

I learned that variations on the salt flotation method helped a couple NY blueberry growers decide when to close this season. After a bad 2017 SWD season, when many NY blueberry growers suffered significant crop loss and shut down early, it was time to take action to monitor their fruit. Here are their methods.

Grower 1.

We analyze a batch of berries picked off bushes and a batch gathered that have fallen to the ground. Blueberries are collected randomly across our 5-acre patch. We test batches of 20-30 berries from these two sources separately and then compare.

Mix a solution of one gallon of water to one cup of salt. Place collected blueberries in two separate, labeled bags. Slightly squeeze the berries to help release larvae. Some say to give it about an hour, but in most cases, if larvae are present, they will show up in the solution as early as 15 minutes. Of course, you will want to use a magnifying device such as a jewelers loop or magnifying glass. You will see small white larvae if infestation is present.

Their results this year:

  • Aug 08:  negative, both from bushes and on the ground.
  • Aug 10:  negative, both from bushes and on the ground.
  • Aug 11:  positive, both from bushes and ground, but more pronounced with the latter.

In 2017, at least once, fruit tested positive for berries that were on the ground, but negative when picked from the bush.

Grower 2.

The salt flotation method we use is basically the same as the method demonstrated at the SWD workshops in 2014-2015. But instead of pouring the salt solution into a low tray and visualizing larvae over a black paper with a hand lens, we pour the solution through a very fine stainless steel mesh permanent coffee filter and check for larvae under a dissecting microscope. It's faster overall, and much easier to find the hard-to-see 1st instar larvae (probably to my detriment, since in the past I could ignore what I couldn't see).

We collect 100 berries randomly from throughout the planting. These are covered with salt solution (1 cup salt in 1 gal water) in a plastic bag. I don't bother pressing on the berries to crack the skins as they suggest, but gave them plenty of time to exit on their own (at least an hour, usually 2 or more).

Results this year, percent fruit with larvae, in our unsprayed blueberry planting:

  • Jul 26: 1.5%
  • Aug 3: 4%
  • Aug 9: 16.5%
  • Aug 11: 30%
  • Aug 13: 78% - in two days, the SWD numbers rose dramatically!

A male spotted wing drosophila (SWD) on blueberry, photographed in early September.

In all cases, collect what appears to be sound, perfect fruit to test for SWD infestation using salt flotation. SWD entrance and exit holes in fruit are less than half a mm in diameter and practically invisible.

I hope these two growers’ experiences using salt flotation will motivate you to monitor your fruit in this way to check for SWD infestation.

There are still a lot of delicious berries out there; lets check them and protect them from this nasty insect!

A national team of researchers lead by the University of Georgia has released a new guide to organic management of SWD this May, 2018, Management Recommendations for SWD in Organic Berry Crops. The guide details information on non-chemical and insecticide approaches to protect berry crops against SWD.

Controlling SWD is particularly challenging, requiring a rigorous, persistent and diverse management plan. The guide details several management recommendations and suggests using as many control techniques as possible to reduce SWD infestation.

Funding for the research was provided by the USDA National Institute of Food and Agriculture Organic Agriculture Research and Extension Initiative (OREI).

Download the guide in PDF form here, http://www.ipm.msu.edu/uploads/files/SWD/SWDOrganicBerryCrops.PDF.

This post was written be Peter Werts, EcoFruit, IPM Institute of North America, Inc.

Strawberry renovation is a critical, but often overlooked part of growing June bearing strawberries.  This year, with SWD numbers climbing, it’s even more important to remove fruit leftover in the field as quickly as possible. Otherwise, this fruit can serve as a food and reproductive resource for SWD population growth.

The task that creates a lag in the renovation process is the 2,4-D application.  Most growers want to apply this herbicide all at once, so early berries are forced to wait weeks for the late varieties to finish — and in the case of ‘Malwina’, growers could delay renovation for more than a month.  This tactic leaves a continuous supply of unharvested, cull fruit that SWD can develop in. A further delay is due to 2,4-D needing to be taken up by the leaves — mowing is delayed for 5 days to allow the weeds to absorb the herbicide.  Given this added delay from choosing 2,4-D, growers need to make sure the weed species in their field are vulnerable to 2,4-D.  If not, don’t delay renovation to use an ineffective herbicide, choose an alternate herbicide, and mow the planting as soon as picking is finished.

Strawberry renovation. Photo: University of Maine Extension.

Whenever possible, mow the variety as soon as harvest is done.  Be aware that mowing a water- or heat-stressed field can result in poor re-growth.  Therefore, make sure the plants are well watered prior to mowing.  If temperatures are above 90 degrees and you cannot irrigate, mowing should be delayed.  If irrigation is not possible, consider skipping the mowing — but still renovate by narrowing the rows and throwing some soil up over existing crowns.

When strawberry fields go out of the rotation, remove them from production as soon as possible by tilling and then seeding a cover crop or a late season vegetable.  If you cannot till the field, then mow it close to the crown or cultivate aggressively to help crush and dry down the remaining berries.  This will help destroy this resource and limit SWD population growth in the remnant fruit.

Renovation Process – Immediately after Harvest is Finished

1. Ensure the field has adequate soil moisture.
2. Apply 2,4-D if needed.
3. Wait 5 days after 2,4-D is applied to mow.  If 2,4-D is not used, mow immediately after picking.
4. Fertilize.
5. Narrow the rows, cultivate middles of wide rows. Throw ½” of soil over remaining crowns.
6. Apply pre-emergent herbicide (ie Sinbar – make sure to read labels as some varieties are sensitive).
7. Irrigate.

For more in-depth information re: strawberry renovation, visit http://www.hort.cornell.edu/fruit/nybn/newslettpdfs/2014/nybn1306.pdf.

This post was written by Laura McDermott and Juliet Carroll, Cornell Cooperative Extension.

Two female SWD were caught in one of two traps set in an Amelanchier hedgerow immediately adjacent to a June bearing strawberry field during the week ending June 25, 2018. The two other traps at this location are inside exclusion netting over a blueberry planting and caught zero SWD. These traps are being monitored by Laura McDermott, Eastern NY Commercial Horticulture Program, Cornell Cooperative Extension.

Two female SWD captured in traps on Long Island on July 9, 2014. The large, armed ovipositor is visible on both, below the black tip of the abdomen.

Strawberry harvest is winding down and there is concern about strawberry renovation practices and potential spillover of SWD into nearby fruit from cull strawberries. Blueberries, raspberries and cherries are ripening and harvests are beginning across New York. Population levels are still low and, so far, no sites are at sustained catch. In addition, few counties across New York have caught SWD — keep an eye on the NY distribution map, because things may change rapidly in the coming week.

It is time to plan your insecticide program for managing SWD. Take this time to determine what insecticides will best fit your overall management program and markets.

What has held back the trap catch this season?
SWD first catch occurred very early this year, but sustained and subsequent increases in trap catch didn't materialize. Environment may have played a roll — weather had intermittent heat waves in May, June was dry, and nights were cool. Last year's serious SWD infestations in blueberries and tart cherries may have made growers more vigilant and willing to invest in insecticide sprays early, keeping populations down.

Why does the SWD population explode?
You can do the math. Let's think optimum conditions for SWD development. A single female can lay around 350 eggs during her lifetime, about 15 per day. The egg to adult phase of the life cycle takes as little as 6 days. So, one female in one day can result in 15 more adults 6 days later, and, during those 6 days, she will have laid another 90 eggs. 6 days after that, those 90 eggs will all be adults. Half of the 105 adults will be females, capable of laying ~350 eggs during their lifetimes...that's 18,375 eggs. A typical life span for SWD is 3 to 9 weeks and there are estimated to be about 10 generations per year in the US, depending on climate.

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