Spotted Winged Drosophila (Drosophila suzukii)


   Male SWD fruit fly, quite small, only 3mm in length, caught in cider vinegar trap.
Note black spots on wings, which are distinguishing characteristics of the male SWD.

 
 

Spotted Wing Drosophila Surveillance Program- Update July 17, 2019

  • Low levels of Spotted Wing Drosophila (SWD) have been found in traps in southern Manitoba.
  • Fortunately saskatoon and strawberry harvesting is underway so hopefully most of the crop will be off the fields before SWD reach economically damaging levels.
  • As more wild hosts and other commercial berry crops begin to ripen, expect SWD numbers to start building up significantly by late July.
  • Berries are susceptible to SWD infestation from the start colour starts to appear on the berry all the way through harvest. Producers have many chemical control options to control SWD (see below)
  • It is important to constantly rotate every application through different insecticide chemical groups to avoid potential insecticide resistance issues with SWD.
 
Berry Crops Most at Risk Now
Raspberries: As raspberries start to change colour and ripen now through the remainder of July, an insecticide could be applied to protect bulk of the harvest which has already started in many fields. Repeat with an alternate insecticide 7-10 days later (see registered controls link below).
 
Late Season June-bearing Strawberries: At risk now would be the later picking of late season June-bearing strawberries, so may not be worth spraying unless significant harvest remaining. 
 
Cultural Control
  • Harvest ripe berries frequently and cool berries quickly after harvest. SWD stop growing in the berry and eventually die at cool refridgerator temperatures.
  • Keep raspberry rows more narrow to reduce favourable habitat for SWD.
  • Remove unmarketable fruit and crush in alleyways.

Chemical Control

  • Weekly application of approved insecticides are quite effective at controlling SWD and protecting the berry harvest from damage. Treatments are available for SWD if detected early, registered control products are listed at: https://onfruit.ca/wp-content/uploads/2019/06/SWD-Registrations-June-2019-V2.pdf
  • This is a guide only, always refer to the product label before applying the product.
  • It is important to constantly rotate every application through different insecticide chemical groups to avoid potential insecticide resistance issues with SWD.

SWD Background Information

Spotted Winged Drosophila (Drosophila suzukii) (SWD) is a vinegar fly of East Asian origin that can cause damage to many soft skinned fruit crops. SWD pierces seemingly healthy fruit, and lays its eggs. The eggs hatch in about 3 days, the larvae feed on the fruit and emerge as adults after 6-28 days. Early detection is critical because symptoms often do not appear until after the fruit is harvested. Commonly confused with the common fruit fly, Drosophila melanogaster, SWD differs as it attacks unripe to ripe fruit, whereas the common fruit fly feeds on overripe and rotting fruit.
 
SWD most commonly affects raspberries, strawberries, blueberries, cherries and plums. It was first identified in Manitoba in commercial berry fields in August, 2013.

 

SWD identification (MSU factsheet)

 
This insect pest has become widely established throughout North America. Spotted wing drosophila adults can be blown by wind to nearby locations or transported to new regions via infested fruit. It has been confirmed in neighbouring regions such as southern Ontario in 2010, Minnesota in 2012 and North Dakota in 2013. In Ontario SWD has been found in traps located near raspberries, blueberries, strawberries, cherries, apricots, grapes, currants, sea-buckthorn, plums and wild hosts. It is unknown whether SWD will overwinter in Manitoba and how early SWD will appear in the following growing season.
 
The Prairie Fruit Growers Association and Manitoba Agriculture Fruit Crops Program are working in collaboration on a SWD surveillance program in the 2019 field season to provide advance warning to commercial berry producers of the presence of SWD and when to start control applications.

 

Berry Salt Test for Larvae

Test berries for larvae using ¼ cup salt in 4 cups of water, place ripe (but not overripe) berries in a pan with the salt solution, gently break-up the berries and look for small, white larvae to float in the solution.  Salt water berry test for SWD link