Insect of the Month - Spotted Wing Drosophila

 
  Hort Snacks - April 2017
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 Causal Agent: Drosophila suzukii

Crops Affected:
Domestic fruit hosts = strawberry, raspberry, blueberry, cherries, peaches, plums, nectarine, honeysuckle, apricot, blackberry, table grape, hardy kiwi;
Wild fruit hosts = elderberry, dogwood, Oregon grape, currant, mulberry
Potential other Alberta host crops – sour cherries, black currant, Haskap / Blue honeysuckle

Life Cycle:

  • Higher risk host crops = softer skinned fruit; later season crops
  • Adults = 2-3 mm light yellow-brown flies with red eyes
    • Males have a single black spot on the end of each wing
    • Females have no spots but have a distinctive, saw-like ovipositor (egg-laying device)
  • Adults may be present from June until November (in some areas)
    • Prefer warmer conditions (20-30°C)
  • Females lay eggs inside intact, ripening fruit
    • Lay over 350 eggs; Eggs develop into larvae in 1-3 days
    • Larvae hatch and feed within the fruit, maturing within approximately 2 weeks
    • Pupae stay within or on fruit for up to 2 weeks
  • May be spread by windblown adults (shorter distances) or transportation of infested fruit (long distances)
  • Overwinter as adult flies
    • Not known to overwinter in Canadian Prairie conditions, however definitely possible in certain microclimates (next to buildings with heat leakage, etc.)
    • Can tolerate high heat and cold winters
Symptoms:
  • Females saw through intact flesh to lay eggs
    • Results in pinprick-sized holes visible in the soft areas of the fruit
  • Larvae feeding within the fruit
    • Fruits soften and collapse when feeding is occurring
    • Rate of collapse is accelerated by multiple larvae
  • Fruit becomes unmarketable
  • Diseases may develop in infested fruit
Adult male SWD - Note wing spots
Adult female SWD - Note saw-like ovipositor
Photos by Sheila Fitzpatrick - AAFC
Fruit damaged by SWD - Note sunken flesh
Photos by BCMAF
Fruit damaged by SWD - Note sunken flesh, oviposition holes, larvae and pupa
Photos by OMAFRA, OSU

Monitoring:
  • Monitor for adults using baited traps from mid-May onward
  • Traps are baited with apple cider vinegar OR yeast and sugar
  • Traps are placed in different areas where adult flies might be found
    • Producing fields
      • May rotate traps into different crops as they reach maturity
    • Locations with ripe fruit – e.g. waste/cull areas; market areas
  • Fruit can also be tested for infestation
Management:
  • Monitor to determine the presence and changes in numbers of adults
  • Ensure good sanitation in fields
    • Clean up leftover or fallen fruit
      • In field, in storage, on equipment
    • Bury 12 inches deep, freeze or solarise infested fruit
  • Cool harvested fruit quickly to slow larval development
    • Apply registered insecticides to control adult flies
      • Apply if trapping indicates presence
      • May need to reduce transfer of populations to later crops
    • Product Choice
      • Most effective active ingredients = pyrethroids, organophosphates, spinosads
      • Neonicotinoids are not effective
 
 
 
 
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For more information about the content of this document, contact Robert Spencer.
This information published to the web on March 27, 2017.