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.
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%.
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, susceptiblefruit 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/.
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.
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/.
Not quite everywhere, but all of the Eastern NY network is now at first or sustained catch and all but four counties in the Lake Ontario, Central, Finger Lakes, and Southern Tier regions are at first catch. That’s seven counties reporting first catch, most from traps checked on June 22!
Cayuga County had 2 males and 2 females in a raspberry field. Checked June 18.
Chemung County had 3 males and 2 females in a blueberry planting. Checked June 22.
Columbia County had 2 males and 3 females in a tart cherry orchard. Checked June 22.
Orleans County had 1 female in a raspberry field. Checked June 22.
Tioga County had 5 males and 3 females in a blueberry field. Checked June 22.
Washington County had 1 male and 2 females I a blueberry field. Checked June 22.
Wayne County had 2 females in a raspberry planting. Checked June 22.
A male spotted wing drosophila (SWD) on blueberry; another likely SWD is in the background.
Fruit across the region is ripening – blueberries, cherries, possibly even raspberries. Other summer fruits like haskaps and June berries are susceptible to SWD. June strawberries could be at risk. Day neutral strawberries will be at risk. Peaches and plums? – pick them before they are deliciously tree ripe and soft.
And now, I’m going to repeat myself.
Pest management for SWD includes:
Mowing – to reduce humidity and niches for SWD harborage and to increase sun penetration.
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.
Monitoring – to know if SWD is present when fruit is ripening.
Sanitation – to reduce reproduction harborage and overall SWD population.
Cold storage – to slow or kill any eggs and larvae in harvested fruit.
Insecticide treatment – Insecticide Quick Guides for NY State:
Exclusion netting over high tunnel raspberries will protect them from SWD.
Those who choose not to spray will have to take every measure possible to prevent population build up. Exclusion netting should be the plan for these growers going forward, because without exclusion netting and without insecticide protection it’s impossible to bring sufficient fruit to harvest in years like 2020 when SWD populations build up early and crop development is delayed.
Clean picking and treating with insecticide to “reset the field” is a management tactic used in large-scale commercial blackberry production in North Carolina. You may want to consider that tactic in your raspberry and blackberry plantings, if SWD has gotten ahead of you. It will only work in such fruit crops that continue to flower and set fruit.
Sustained catch, that is two weeks in a row, was obtained in two counties in Eastern NY, Ulster on June 19 and June 21 and Albany on June 22. Indeed, SWD catch was prevalent across New York State’s monitoring network in traps checked at the end of last week and early this week.
Ulster site 5 had 1 male and 1 female in a blueberry field – fruit is ripening and will need to be protected. Checked June 19.
Ulster site 6 had 4 males and 2 females in a raspberry planting – pink fruit will be picked clean and an insecticide applied to reset the field. Checked June 19.
Ulster HVL had 5 males and 11 females in a cherry orchard – fruit is ripening and will need to be protected. Checked June 21.
Albany had 10 males and 26 females in a raspberry field – ripening fruit will need to be protected. Checked June 22.
Fruit of tartarian honeysuckle, also considered an invasive plant in NY, can support SWD development.
Are you seeing a pattern? With numbers this high, it will be imperative to begin a spray program to protect fruit. SWD populations have built up just as fruit are beginning to ripen. This translates into a challenging year for SWD management.
Those who choose not to spray will have to take every measure possible to prevent population build up. Exclusion netting should be the plan for these growers going forward, because without exclusion netting and without insecticide protection it’s impossible to bring sufficient fruit to harvest in years like 2020 when SWD populations build up early and crop development is delayed.
Clean picking and treating with insecticide to “reset the field” is a management tactic used in large-scale commercial blackberry production in North Carolina. You may want to consider that tactic in your raspberry and blackberry plantings, if SWD has gotten ahead of you. It works best in such fruit crops that continue to flower and set fruit season-long.
Thanks go out to Jim O’Connell, Ulster County CCE who is monitoring Ulster 5 and 6; Lydia Brown, Hudson Valley Research Laboratory, who is monitoring Ulster HVL (traps set in honeysuckle were at first catch this past week, too – one female); and Natasha Field, ENYCHP CCE, who is monitoring the Albany County site.
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 andJanet 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.
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.
As in "exclusion netting"...? Here are answers to growers' most frequently asked questions.
In organic and low spray vegetable production, insect exclusion netting, for many years, has successfully reduced or eliminated insect pest damage. The arrival of spotted wing drosophila (SWD) and the devastation it caused prompted immediate field research on this barrier method for berry crops. Since 2013, NY farmers, Cornell University and Cornell Cooperative Extension, have gathered field data on the effect of netting on SWD populations and the crop itself. You can read two Fruit Quarterly articles about this work:
Exclusion netting over high tunnel raspberries will protect them from SWD.
Growers should keep in mind that no outcome in farming – from pest control tactics to markets – is guaranteed. Below we give straightforward answers, gleaned from seven years of experimenting with SWD exclusion netting, to your frequently asked questions.
What is exclusion netting?
Insect exclusion netting is woven from polyethylene yarn in a variety of weaves. Looser weaves are lighter and allow more air through, but the space between fibers allow smaller insects to pass through. In field trials 60 gram netting (mesh size 1.95 x 0.95 mm) did not exclude SWD. 80 gram netting (mesh size 1.0 x 0.6 mm) has repeatedly excluded SWD over several production seasons. There is an 85 gram netting available for situations that require additional durability – that weave will exclude SWD as well. Some manufacturers are selling 70 gram netting for SWD exclusion, however, none of the Cornell studies tested 70 gram netting in the field. The nets come in different widths and lengths depending on the manufacturer. Some manufacturers will sew panels together, some offer zippered panels etc.
Does it work?
The simple answer is YES! 100% exclusion of SWD can be achieved IF:
nets are put up early, before SWD appears
nets have no holes or gaps
nets are managed and maintained effectively throughout the season
and a well-designed entry way is used.
There is always a chance that SWD will get inside and it can be a problem requiring some sort of treatment. But, overall, our experience suggests this is uncommon when growers are diligent with their installation of exclusion netting. This means that pesticide sprays to control SWD and keep fruit clean will be dramatically reduced, and very possibly eliminated, by diligent use of exclusion netting.
Effectively managed exclusion netting will also provide 100% control of bird predation. Growers using the netting have also observed protection from hail, heavy rain and damaging winds. It cannot be overemphasized that, the management of the netting is important to achieving excellent crop protection results.
A wild pollinator feeding on a fall raspberry flower. Keep in mind your crops pollination needs under the exclusion netting.
Is exclusion netting difficult to manage?
Difficult to answer. Depends on the individual farmer. Crop exclusion falls under the general category of protected culture – that is using physical structures and plastic or nets to protect crops from pests and weather instead of complete reliance on pesticides. There is no question that growing crops in any protected culture system from high and low tunnels to exclusion netting requires more attention to detail, a willingness to try something completely different, and commitment to successful adoption.
Netting is quite easy to put in place once the initial system has been designed. There are several ways to winterize the material. Remove it after fruiting to increase its longevity by protecting it from UV degradation.
For perennial crops, few “ready to use kits” exist, because the concept is so new – although that’s changing quickly! Cornell and the University of Vermont have created plans for exclusion net support systems and have spearheaded efforts to include exclusion netting systems in cost-share plan policies, similar to those for high tunnels.
Growers must consider their unique production requirements. You-pick farms need to consider customer access in and out of the exclusion netted field. Farmers may want to leave enough space to get mowers and other larger equipment under the net. If the farm is located in a very windy area support systems should reflect that reality.
How much does the exclusion system cost?
The netting support system will vary from one farm to the next until manufactured kits or standardized plans are created. The current estimate for purchasing netting and the support system, with labor for construction included, would be approximately $10,000 per acre. Given that netting will provide bird control, and the estimate for bird related loss is almost 1/3 of the crop, exclusion netting could be a great investment. The netting itself will last 7-10 years; the support system probably much longer.
Will exclusion netting impact my crop in unexpected ways?
The short answer – no, not that we can determine. After six seasons of netting a commercial blueberry planting in eastern NY, no negative impacts on the plants or the crop have been found associated with the netting. Indeed, anecdotally, netting may enhance blueberry productivity, although more research is needed. Results with raspberries in a high tunnel with netting applied to the tunnel sides and ends show promise – with the caveat for growers to increase the height of sidewalls, use fans and possibly shade cloth to prevent excess heat.
High tunnel raspberries.
Is netting only useful for small acreages?
No. Exclusion netting can be used on all scales of plantings. The requirement being a commitment to using this technology combined with a market that will recoup the investment. Across the globe, protected systems like this are being used for very large acreages. Given the sizable investment for a large scale air-assisted sprayer, if exclusion netting allows a farmer to not have to make that investment – it might even be a savings.
Where can I get exclusion netting? Berry Protection Solutions is the U.S. distributor for the product that Cornell has worked with. There are other products available from other farm supply distributors. More information on protected culture with links to suppliers, research papers and extension support can be found at the Tunnelberrieswebsite.
1 McDermott, L., L. Nickerson, New York Fruit Quarterly, Vol 22, Number 1. Spring 2014.
2 Riggs, D., G. Loeb, S. Hesler, L. McDermott, New York Fruit Quarterly, Vol 24, Number 2. Summer 2016.
This post was contributed by Laura McDermott, ENYCHP CCE, Greg Loeb, Entomology Cornell AgriTech, and Juliet Carroll, NYSIPM CCE.
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.)
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.
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!
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.)
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.
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.
Refer to the Cornell Pest Management Guidelines, cropandpestguides.cce.cornell.edu/ and always have the latest version -- the 2019 version for Berry Crops.
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
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.
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.
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.)
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.
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.
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.
