Author: jec3@cornell.edu

Sustained catch with 2 females and 1 male SWD in a jar trap set on the edge of the summer raspberry planting. Fruit are ripe and SWD has arrived at this planting. Therefore, management programs must be initiated there. These traps are being monitored by Jim O'Connell, Ulster County Cornell Cooperative.

Across NY State, not many SWD have been caught. As seen on the distribution map, only a few counties have reported SWD. The early reports in May were not followed by sustained captures at those sites and SWD numbers are still quite low.

SWD Management entails 5 key tactics:

• 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.

• 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.

• 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, such as raspberries and blackberries, are ripening. 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 are on the SWD Management web page, fruit.cornell.edu/spottedwing/management/. Check the Cornell Guidelines for your crop (cropandpestguides.cce.cornell.edu/) for the latest list of approved pesticides. Always read and follow the pesticide label instructions.

• 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.

• Cool berries immediately.

Chilling berries immediately after harvest to 32° – 34° 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.

Two female SWD were caught during the week ending on June 14, 2021 in a tart cherry orchard in Washington County. The insects were caught in one of two jar traps with drowning solution; two sticky card traps at the site caught no SWD. This site is being monitored by Laura McDermott, Eastern NY Commercial Horticulture Program of CCE.

Across the state, tart and sweet cherries are starting to color. Two sweet cherry orchards in the Finger Lakes had bright red, still hard, fruit throughout. Bird deterrents are going out and bird damage was seen. This signals that sweet cherry blocks may be at risk of SWD infestation... if SWD is in the orchard.

Once cherries begin to ripen, starting around first blush, they will become increasingly susceptible to SWD damage, and applications of effective insecticides will be necessary to keep this pest in check through harvest.  The SWD insecticide quick guide for stone fruit & grapes has just been revamped for 2021, and is available online here on the SWD Management page of Cornell Fruit Resources.

Spray intervals should be tight, no more than a 7-day interval. Applications should also be reapplied if there is any rainfall.  Make sure you rotate the insecticide modes of action (IRAC groups) to prevent insecticide resistance in SWD. Although SWD has been somewhat slow to arrive and build up this year, if your orchard has been troubled by SWD infestation in the past, pay close attention to your insecticide program. When choosing insecticides to manage plum curculio and the cherry fruit flies, select those that are also active against SWD by cross referencing with the SWD insecticide quick guide.

MSU Degree Day Model for SWD Risk in Cherry

To help determine your blocks’ susceptibility and when to begin insecticide treatments, you can use the new MSU degree day model. The model (DD base 4°C BE) predicts cherry fruit ripening (Zavalloni et al. 2006. J Amer. Soc. Hort. Sci. 131: 601-067). The adaptation for SWD, out of Dr. Larry Gut’s and Dr. Nikki Rothwell’s labs at MSU, clocks risk windows for when fruit is soft enough for SWD to lay eggs in it.  This model has been field validated for tart cherry and looks promising for sweet cherry. It is now available on Enviroweather in Michigan. We can apply it in NY by using the Degree Day Calculator on NEWA. newa.cornell.edu/index.php?page=degree-day-calculator

To clock fruit susceptibility in cherries, degree days (DD) are accumulated starting at the full bloom date.  Tart cherries were in full bloom on May 2-3, across much of the Lake Ontario region.

• Low risk – 400 to 529 accumulated DD 4°C BE (no infestation)
• Moderate risk – 530 to 649 accumulated DD 4°C BE
• High risk – 650 to 1000 accumulated DD 4°C BE

Portions of this blog were contributed by Michael Basedow, mrb254@cornell.edu, Eastern NY Commercial Horticulture Tree Fruit Specialist.

During the week ending on June 14, 2021, one male SWD was caught in a raspberry planting in Essex County. The insect was caught on a red sticky card trap. There are four traps set on this site. The traps are being monitored by Andy Galimberti, Eastern NY Commercial Horticulture Program of CCE.

At another location, in the Lake Ontario region, raspberries were seen that were starting to color. The grower at this location thought that was early for his farm. Make sure you watch crop development.

In lab studies, when female SWD are given no other choice but a fruit that is beginning to ripen, she can lay eggs in that fruit.

This is the time to prepare for SWD management and to focus on cultural controls, making sure everything is in tip top shape.

• Canopy, irrigation, and weed management will all make the environment in the planting less favorable for SWD - keeping it sunnier, dryer, and airier.
• Plan to refrigerate fresh fruit upon harvest and make sure your coolers are in good working order. Raspberries and blueberries tolerate very low temperature storage, but SWD can't.
• Practice excellent sanitation of cull fruit - eliminate it so it provides no food or reproductive resources for SWD.
• Consider exclusion netting - feasibility, price, construction. Read about it in this blog, "Thinking exclusion?" blogs.cornell.edu/swd1/2020/03/27/thinking-exclusion/
• Practice regular fruit sampling at each harvest and assess the fruit for larvae using salt flotation.
• Devise an insecticide program to protect fruit. The insecticide quick guides have been updated for 2021. Find them on the SWD Management page.

Sustained catch of SWD was obtained in a blueberry planting in Tioga County on June 9, 2021. However, numbers caught were down from the previous week's seven SWD, with only one male caught in the four traps.

Blueberries may begin to ripen in the coming weeks, so it's time to keep an eye on the crop and review SWD management strategies. Take a look at the information on Cornell Fruit Resources' SWD Management page, fruit.cornell.edu/spottedwing/management/.

Traps in the blueberry planting are being monitored by Barb Neal, Cornell Cooperative Extension of Tioga County.

A single female SWD was caught in a raspberry planting in Ulster County on June 10, 2021. There are two Scentry jar traps and two Trece sticky card traps in the planting. The female was caught in a jar trap. Traps at this location are being monitored by Jim O'Connell, Cornell Cooperative Extension of Ulster County.

The female's egg-laying structure is the problem. It is like a tiny saw blade and allows her to cut through the skin of perfect, ripening and ripe fruit to lay her egg underneath the skin. Inside the fruit, the larva hatches out of the egg and is in a perfect, protected place to develop. After three instars, the larva exits the fruit and pupates. Adult flies emerge from the pupae to mate and lay more eggs.

You can see from the above life cycle, that it only takes as few as 10 days, under optimum conditions, for SWD to grow up from egg to adult. Yikes! No wonder the population explodes in late summer.

Establishing a new balance; disrupting ecosystems

Let's hope that, as the years roll along, our native parasites, parasitoids, pathogens, and predators will learn how to "use" this abundant SWD resource and the population explosions will be moderated, making it easier to protect our fruit.  

Did you know that, in the wild, SWD decimates the wild brambles that birds rely on for food during their post-breeding and fall migratory periods? Research on SWD's impact on bird communities is underway in the Allegheny National Forest in PA, led by Dr. Christopher Lituma, West Virginia University, Morgantown, WV.

Here's hoping a new balance is established to rein in SWD.

I didn't catch this until now! First catch of SWD was obtained last week on June 1, 2021 in a blueberry field in Tioga County by Barb Neal, Cornell Cooperative Extension of Tioga County. In four Scentry jar traps, 7 SWD were caught, 3 males and 4 females. No SWD males were caught on the two sticky card traps also set in the fields.

Last week many blueberry plantings still had some late bloom, though fruit had set and was sizing. This week, fruit has sized up and the crop is looking very promising, but still green without any blush. There is no need to treat specifically for SWD at this stage, because fruit isn't yet susceptible.

Most sites in the monitoring network are still at zero catch and those that had first catch early haven't reached sustained catch. The hot, dry weather may have inhibited SWD activity and development. But that is likely going to change, so stay tuned and keep a watch on your fruit.

The tree fruit and grape SWD insecticide quick guide is updated, as of June 2, 2021. The other quick guides will be updated soon.

The first week traps were set out, a single female SWD was caught in one of the four traps. This is another site in the network without zero catch. These traps are in a blueberry panting, which was at about 50% bloom when traps were checked on May 20, 2021.

Is this a wake-up call? Could be. The SWD insecticide quick guides still need updating, that will be a top priority for next week.

Pollinators are out and about, so think before you spray and protect those important fruit workers. Wild or domesticated, we need their services to harvest the delicious fruits that grow in our region.

Need a refresher on SWD?

Here are the Cornell Fruit Resources web pages to bookmark:

• SWD Home, https://fruit.cornell.edu/spottedwing/
• SWD Monitoring, https://fruit.cornell.edu/spottedwing/monitoring/
• SWD Identification, https://fruit.cornell.edu/spottedwing/identification/
• SWD Management, https://fruit.cornell.edu/spottedwing/management/
• SWD Distribution Maps, https://fruit.cornell.edu/spottedwing/distribution/

There is so much online about SWD; use your favorite search engine to find more on SWD. Get ready! Get set! It's a "Go!"

Starting the season early...with no zero catch at this site...a lone male SWD was caught in a Scentry drowning trap on Monday, May 10, 2021. These traps are being monitored by Elizabeth Tee, Lake Ontario Fruit Program. All four traps at this location are set on the edge of the planting - two drowning jar traps and two red sticky card traps.

The blueberry planting is very close to Lake Ontario in Niagara County. Earlier trap catch of SWD has been obtained in cherry orchards close, within a mile, to Lake Ontario, as compared to inland orchards. Perhaps the Lake microclimate is at play in enhancing overwintering or spring activity of SWD.

Planning to use Trécé Pherocon red sticky cards and lures? You'll only identify the males, so the male SWD characteristics to keep in mind are:

1. The black spots from which the fly gets its common name. One on each wing, along the leading edge, circular to oval, sometimes with faint dark gray stripes within the spot.
2. The two combs on each of the forelegs. These will appear like black dots, but under high magnification, the teeth of the comb can be seen. These black combs' "teeth" run roughly parallel to the length of the leg.

Brush up on SWD identification on the Cornell Fruit Resources SWD Identification page, fruit.cornell.edu/spottedwing/identification/.

Although one male was caught, there's no fruit ripening, so no insecticide use at this time is needed against SWD. Keep monitoring.