Spotted Wing Drosophila

Now found in 25 of 28 (89%) of Counties in the SWD monitoring network, 2015 will be challenging for late fruit crops in NY. Traps have caught SWD two weeks in a row in 22 of the 25 NY Counties reporting SWD finds.

Of the 48 monitoring sites across NY, only 5 have not yet caught SWD; 90% of all SWD monitoring sites have positive reports of SWD caught in traps.

Some monitoring network participants are sampling fruit, when SWD is first caught in traps, and checking for infestation with salt floatation.  At first trap catch, most fruit samples have few to no SWD larvae or eggs in a 50-fruit sample. Monitor your fruit for symptoms and signs of SWD infestation using the methods described in the blog, Do my fruit have SWD?

Those sites where SWD hasn't been caught yet are characterized as having fruit that is not yet ripe, such as fall raspberry, or low fruit set possibly due to the cold winter, such as in blueberry.

Some monitoring sites reported high numbers of SWD in late July/early August, the second consecutive week of trap catch - e.g. 83 in Washington County, 40 in Cayuga County. Cooperators are pulling traps once at sustained catch.

Researchers in Greg Loeb's lab, Department of Entomology, Geneva, studying different lures in the Finger Lakes region are now catching 20-40 SWD per trap. Sites in their study with rigorous spray schedules catch less than 10 SWD per trap. Research projects are wrapping up, too.

Our focus is to provide early warning of SWD arrival in NY State. We will continue reporting on the SWD monitoring network until all sites have caught SWD. If you have any questions, suggestions or comments, please let me know.

14 SWD were caught today, August 17, 2015, in traps set in blueberry in Clinton County, 10 males in traps set in the interior of the crop and 4 males in traps set on the edge of the crop. These traps are being monitored by Lindsey Pashow, technician, and Amy Ivy, educator & director, Clinton County Cornell Cooperative Extension. These males may be lonely...? Another review of trap contents on Wednesday will confirm whether females are absent.  Regardless, don't think for a minute that absence of females means your crop is safe. They could be out laying eggs and ignoring the lure of food provided by the traps. Only three Counties in the 29-County network have not yet caught SWD (Columbia, Dutchess, and Steuben). If your crop is ripe - take steps to manage SWD. If your crop is on the verge of ripening - make plans to protect it from SWD. (GDD = 1793, day length = 13:55)

One female SWD was caught on August 5, 2015 in a trap set in a blueberry planting in Herkimer County. Traps at this location are being monitored by Bernie Armata, Herkimer County Cornell Cooperative Extension Association. (GDD = 1601, day length = 14:18)

To date, only four counties (Clinton, Columbia, Dutchess, and Steuben) have not caught SWD. In these sites, fruit is either unripe or the crop is blueberry, which can be tricky for trap catch with our current traps.

Two SWD at one location & one SWD at a second location in Tioga County were caught the week of August 3, 2015. At both locations the traps were in raspberry and are being monitored by Michele Kline, Regional Fruit & Vegetable Specialist, Tioga County Cornell Cooperative Extension. (GDD = 1562 & 1740, day length = 14:10 & 14:09, respectively.)

One male SWD was caught on August 4, 2015 in a trap set in fall raspberry in southern Essex County. The report comes in from Amy Ivy, Clinton County Cornell Cooperative Extension and Eastern NY Horticulture Program. The raspberries at this site are just starting to ripen. (GDD = 1602, day length = 14:24)

In response to Amy's finding, Laura McDermott replied, "The pressure we are experiencing (in the Capital District) right now makes me want growers to be as pro-active as possible. The fact that you found (SWD) in a crop that hasn’t even started harvest yet is significant – and I would advise people to get ready to start spraying. I’ve been getting calls from around the state from folks that are seeing (SWD) that haven’t really been bothered much since 2012."

2015 is going to be a challenging year for SWD management. It is time to take SWD management seriously.

One female SWD was found on August 4, 2015 in a trap set in blackberries in Saratoga County. This report came in from Tegan Matthews, Cornell Cooperative Extension Intern with Laura McDermott, Eastern NY Horticulture Program. (GDD = 1863, day length = 14:19)

The blackberries at this site are almost completely devoid of fruit! But, it looks like SWD will be on hand to infest fruit once it develops unless it is protected with insecticide. Plan on an effective, well timed spray program for your fall berries; refer to the berry insecticide guide for SWD. Make sure you rotate between different insecticide modes of action (or IRAC groups) to prevent insecticide resistance from developing in SWD. Pay attention to all management practices for SWD to lower the risk of fruit infestation.

Two female and one male SWD were caught on Thursday, July 30, 2015, in a trap set in raspberry in Chemung County. Traps in this county are being monitored by Michele Kline, Regional Fruit & Vegetable Specialist, Tioga County Cornell Cooperative Extension. No SWD were caught in a trap set in blueberry at this location. (GDD = 1459, day length = 14:26)

SWD populations are building up. Of the 44 locations where traps are being monitored for SWD, 29 (66%) have reported SWD trap catch. Over half of these locations have caught SWD two weeks in a row with SWD numbers caught now in the teens. Sixteen locations in Albany, Cayuga, Genesee, Niagara, Ontario, Rensselaer, Schuyler, Ulster, Wayne and Yates Counties are at sustained trap catch—two weeks in a row. Monitoring for first catch of SWD is nearing completion for 2015 and traps are being pulled from the monitoring network.

SWD populations are increasing in neighboring states and provinces, too. Reports from Ontario Province and Maine, Massachusetts, and Rhode Island align with our findings in New York State. If you are in affected counties, take measures to protect your fruit crops – insecticide programs, sampling fruit, sanitation, and postharvest refrigeration will all assist in protecting susceptible fruit.

Be proactive with your customers. Let them know about SWD and what you are doing to combat it. Tell them to refrigerate the fruit they buy.

Reports of SWD eggs and larvae are coming in from our research and Extension colleagues. You can check for fruit infestation using a salt floatation test. Follow these methods:

• Prepare salt water – 1 cup salt per gallon of water.
• Collect perfect fruit. Fruit should be sale-able, not soft or overripe. (25 large – strawberry, plum; 50 medium – large-fruited blueberry or blackberry; 75 small – small-fruited blueberry or raspberry.)
• Put fruit in a gallon size re-sealable plastic bag.
• Pour salt water into the bag to cover the fruit.
• Mark bag with field code and date.
• For a quick check in the field – after 15 minutes, hold the bag up to light. This helps to see the larvae that emerge from the fruit into the salt water.
• For a more thorough examination – after 15 minutes, pour the fruit and salt solution into a shallow tray and use a piece of wire mesh screen to hold the fruit down or sieve it to separate the larvae in the salt water from the fruit. Larvae are more easily seen against a dark, black background. The better the lighting, the easier it will be to see the larvae, so plan to be in a well-lit area with minimal glare.

NOTE - A light infestation, or one with mainly 1^st instar larvae, will be difficult to see with the naked eye. Use a magnifier, loop, hand lens, optivisor, or dissecting microscope for easier viewing. Another approach is to split the fruit sample into two parts – do salt floatation on one part and hold the other part in a container at room temperature and do salt floatation on it after three days.

First instar larvae are < 1 mm long. Third instar, fully grown larvae are 2-3 mm long. SWD larvae (Drosophila suzukii) are indistinguishable from larvae of the common vinegar fly (D. melanogaster.)

A video on salt floatation in the field, produced by Peerbolt Consulting, Pacific Northwest, can be found at: http://www.berriesnw.com/videos/baggieTest/2010SaltBagTest.htm

If an infestation is found in your planting, clean pick all ripening, ripe and overripe fruit into clear re-sealable bags. Kill the SWD in it by freezing it or solarizing it and dispose of it. Pick up or step on and crush any fruit that has dropped to the ground. Protect the unripe fruit with insecticide sprays applied at 5 to 7 day intervals. This practice will protect the green and unripe fruit from the SWD that would have developed in the infested fruit in the planting and dropped on the ground.

If your berry planting is small and can be framed over, consider the use of exclusion netting to protect fruit next year. This may be worth the investment to preclude the need for routine insecticide applications.

Four male and 10 female SWD were caught on Monday, July 27, 2015 in traps set in red raspberry in Monroe County. All four traps at the site caught SWD. For berry crops that are at risk of infestation, it will be important to plan a spray program and sanitation program to protect ripening fruit. Cool fruit (32-33 F) as soon as possible after harvest to delay or stop development of SWD. This information, and more, is available on the SWD Management page on Cornell Fruit Resources.  (GDD = 1590, day length = 14:40)