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Sustained Catches, More SWD

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

Sustained catch on June 29

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

Sustained catch on July 2

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

Sustained catch on July 7

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

Sustained catch on July 14

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

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

Aggressive management entails 5 key tactics:

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

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

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

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

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

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

Quick reference guides:

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

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

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

A salt flotation method, immersing fruit in a solution of 1 Tbsp. (14.8 cc) table salt per 1 cup (236.6 ml) water, may cause larvae to float to surface. At least 100 fruit per block per harvest should be observed for infestation. Suggested methods were adapted for NY growers in Guidelines for Checking Fruit for SWD Larvae in the Field (

  1. Cool berries immediately:

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

Learn more about SWD. Check out the information on Cornell Fruit Resources Spotted Wing Drosophila,

Thanks go out to:

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

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