UMass Extension Fruit Advisor Program

Spotted Wing Drosophila (Drosophila suzukii)

Male Spotted Wing Drosophila (Drosophila suzukii)

Background

Spotted Wing Drosophila (Drosophila suzukii), SWD, is a recently introduced new species of fruit fly in the United States. It was first found on the west coast in 2008, but has rapidly colonized many fruit producing regions of the country. It was found in New England in late summer 2011 shortly after Hurricane Irene and caused significant crop damage in fall raspberries among other crops. While fruit flies (or vinegar flies) are nothing new in the US, this species is different in it's ability to infest healthy fruit. Other species typically infest over-ripe or damaged fruit. Females of this species have serrated ovipositors that can cut into healthy fruit to insert eggs. This can lead to problems with deteriorating fruit in the field or with customers who find multitudes of larvae in fruit after harvest.

Crops at Risk

This insect has a wide host range but is primarily a pest of berry crops and some stone fruits (cherry, nectarine, peaches), but may also be found in high tunnel tomatoes.

Crop Host Crop Host Wild Host
Apple Grapes American Pokeweed
Asian Pear Italian Plums Autumn Olive
Asian Plum Mulberries Beach Plum
Blackberries Nectarines Climbing Nightshade
Blueberries Peaches Crabapple
Boysenberries Persimmons Fox Grape
Cherries Plumcots Japanese Yew
Cold Hardy Kiwis Raspberries Kousa Dogwood
Elderberries Strawberries Porcilainberry
  Tomatoes Wild Rose

Identification/Lifecycle

The first step in dealing with this new pest is identification. Spotted Wing Drosophila is a small vinegar fly. Both males and females have red eyes. Males have two spots on their wings, which is a key identifying feature. Females lack the wing spots but have a robust and serrated ovipositor that distinguishes them from other species of fruit fly. Seeing the ovipositor requires some magnification; a hand lense will do.

  • Overwinter as adults and maybe pupae in leaf litter, duff, and rotting fruit
  • Adult flies live for up to 2 weeks
  • Females can lay 300 eggs
  • Can develop from egg to adult in as little as 8 days
  • Likely to have over 10 generations per growing season

Damage:

  • Females lay eggs in fruit
  • Larvae eat flesh, which renders it unmarketable or causes customer discontent (infested fruit ‘melts down’ in 2 days)
  • Egg laying introduces fungal pathogens, which rot fruit

Significance:

  • Unlike other fruit flies, SWD attacks sound ripening fruit
  • Once eggs laid in fruit, no longer able to control with pesticides
  • Short lifecycle and overlapping generations make spray timing difficult
  • Requires sprays near harvest time
  • Requires multiple sprays which can lead to pesticide resistance

Management:

Monitoring

  • Use traps to establish presence and abundance of SWD
  • Set traps out prior to fruit ripening to establish onset of infestation
  • Check traps frequently (at least once per week)
  • Replaice bait weekly to maintain effectiveness (don't dump old bait on ground; remove from field)

Identification

  • Use sticky cards inside traps or sieve contents to and check to confirm presence of SWD (males are easiest to see)
  • Use hand lense and ID key to help with ID
  • Record date and number of SWD caught to determine trend

Control

Sanitation - keep area free of overripe fruit to reduce habitat for build up; eliminate wild hosts as much as possible

Exclusion - small areas can be covered with fine netting or row covers prior to fruit ripening to keep SWD out

Biological Control - researchers are looking for suitable predators, parasitoids, pathogens and other beneficial organisms that might help suppress SWD populations.

Chemical Control - use of short residual pesticides (organic and conventional) are likely the most effective short term solution for this pest.

Table 1. Insecticides for Blueberries, Strawberries, Caneberries, Grapes and Stone Fruit for Spotted Wing Drosophila

Active Ingredient Trade name1 IRAC code Blueberry PHI (days) REI Caneberry PHI (days) REI Strawberry PHI (days) REI Grapes PHI (days) REI Stone Fruit PHI (days) REI Probable Efficacy
Carbaryl Sevin 1A 7 12 hrs 7 12 hrs 7 12 hrs 7 12 hrs 3 12 hrs Good
Diazinon Diazinon 1B 7 5 days 7 5 days 5 3 days Not labeled Not labeled 21 4 days Excellent
Malathion Malathion 1B 1 12 hrs 1 12 hrs 3 12 hrs 3 24-72 hrs 1 or 3 12 hrs Excellent
Methomyl Lannate 1A 3 48 hrs Not labeled Not labeled Not labeled Not labeled Not labeled Not labeled Not labeled Not labeled Excellent
Phosmet Imidan 1B 3 24 hrs Not labeled Not labeled Not labeled Not labeled Not labeled Not labeled 7 3 day Good
Bifenthrin Brigade 3 1 12 hrs 3 12 hrs 0 12 hrs Not labeled Not labeled Not labeled Not labeled Excellent
Esfenvalerate Asana 3A 14 12 hrs 7 12 hrs Not labeled Not labeled Not labeled Not labeled 14 12 hrs Excellent
Fenpropathrin Danitol 3 3 24 hrs 3 24 hrs 2 24 hrs 21 24 hrs 3 24 hrs Excellent
Pyrethrin Pyganic* 3A 0 12 hrs 0 12 hrs 0 12 hrs 0 12 hrs 0 12 hrs Good
Zeta-cypermethrin Mustang Max 3 1 12 hrs 1 12 hrs Not labeled Not labeled 1 12 hrs 14 12 hrs Excellent
Imidacloprid & cyfluthrin Leverage 360 & 2.7 4A, 3 Not labeled Not labeled Not labeled Not labeled Not labeled Not labeled 3 12 hrs 7 12 hrs Excellent
Actamiprid Assail 4A 1 12 hrs 1 12 hrs 1 12 hrs 7 12 hrs 7 12 hrs Fair
Imidacloprid Provado†† 4A 3 12 hrs 3 12 hrs 7 12 hrs 0 12 hrs 0-7 12 hrs Fair
Thiamethoxam Actara 4A         3 12          
Spinetoram Delegate 5 3 4 hrs 1 4 hrs Not labeled Not labeled 7 4 hrs 7 4 hrs Excellent
Spinetoram Radiant 5 Not labeled Not labeled Not labeled Not labeled 1 4 hrs Not labeled Not labeled Not labeled Not labeled Excellent
Spinosad Entrust*,†† 5 3 4 hrs 1 4 hrs 1 4 hrs 7 4 hrs 1 - 14 4 hrs Good/Exc
Pyriproxyfen Esteem 7 7 12 hrs Not labeled Not labeled 2 12 hrs 21 12 hrs 14 12 hrs Fair/Good

*OMRI listed

†† Stone Fruit: there are different PHI depending on specific stone fruit crop, check label before using

PHI= pre-harvest interval; time between last application and harvest

REI= re-entry interval; time between application and when workers may re-enter the field

Probable ratings based on lab and field assays in western USA and Michigan

Chart courtesy of Mary Conklin, UConn Extension

However:
  • Requires a short pre-harvest interval (PHI)
  • Requires > 5 day residual activity
  • Requires rotation among mode of action (MoA) to avoid developing resistance