Damage

Vinegar flies typically attack rotting or fermenting fruit and will not damage healthy fruit. However, SWD will attack fresh, healthy fruit.  Female SWD are able to attack healthy fruit due to the presence of a reinforced, serrated ovipositor which allows her to cut a slit into healthy fruit to lay eggs.  Other vinegar flies lack this serrated ovipositor and cannot penetrate the skin of intact fruits.

Figure 1 – SWD Larvae

Photo Credits: Phil Pellitteri, UW-Madison Insect Diagnostic Lab

Figure 2 – Damage in Raspberry

Photo Credits: Parent, Whitney, Shearer, Reitmajer, Dalton and Walton; USDA-ARS Corvallis and Oregon State University

Figure 3 – Damage in Strawberry

Photo Credits: Parent, Whitney, Shearer, Reitmajer, Dalton and Walton; USDA-ARS Corvallis and Oregon State University

Figure 4 – Damage in Cherry

Photo Credits:
1 – Martin Hauser, CDFA
2 – Michigan State University Extension
3 – UC Statewide IPM Program, Copyright 2009 Regents, University of California

 Initial signs of SWD infestation are small scars left by the female’s serrated ovipositor.  Once the eggs hatch, larvae feed within healthy fruit tissue causing adjacent tissue to collapse within a few days; consequently crop loss may be severe.  This damage causes considerable softening of the fruit.  Damaged fruit is difficult to harvest and is generally unmarketable.  Secondary pathogens may also be introduced at the larval feeding sites which cause additional deterioration of the fruit.

Host Plants

Figure 5 – Host Plants

Photo Credits: (left to right) 
1 – Martin Hauser, CDFA
2 – Hannah Burrack, NC State, Bugwood
3 – Hannah Burrack, NC State, Bugwood

SWD have a wide host range and prefer soft skinned fruits, including: blueberries, strawberries, raspberries, cherries, blackberries, grapes, peach, plum, tomatoes and melons. While apples may be at risk, damage to healthy apples has not been reported.  Damage has not been reported on cranberries, but may be possible.  Damage has also been noticed on some specialty crops such as goji berries and Sea-buckthorn.  

Recent research has identified several alternative host plants present in the wild: bush honeysuckles (Lonicera spp.), wild cherries (Prunus spp.), buckthorns (Rhamnus spp.), and dogwoods (Cornus spp.).  The concern with alternative host plants is that they may serve as alternate food sources for SWD populations.