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Wednesday, September 1, 2010

SWD trapping update - Identification overview

One male spotted wing drosophila (circled) and 3 non SWD. Trap from Davidson County, NC. Photo: HJB
Drosophila suzukii (spotted wing drosophila) trap captures are increasing throughout the Carolinas. Last week, SWD were confirmed from our monitoring site in Davidson County, NC, and we continue to catch flies at 7 other locations in NC and SC. The table below summarizes these locations and the total flies detected to date. See here for links to trap capture data for all of the southeast monitoring locations.

Site
Date of first capture
Total flies to date
Davidson County, NC
8/24/2010
19
Edgecombe County, NC
7/30/2010
1
Lexington County, SC
(Site 1)
7/30/2010
6
Lexington County, SC
(Site 2)
8/6/2010
19
Spartanburg County, SC
8/13/2010
4
Saluda County, SC
7/2/2010
5
Randolph County, NC
7/27/2010
9
Montgomery County, NC
8/11/2010
17

In addition to SWD, several other flies have been caught in the traps, many of which can be confused with SWD. The image above includes 1 male SWD with clearly visible wing spots (circled) and 3 other flies which could be confused with SWD. The image below notes the key characters to distinguish between these 3 flies.

Non SWD flies. Left: fly with "cloudy" cross veins (cross vein circled). This cross vein will not be cloudy in SWD wings. Center: fly with spotted abdomen. SWD will have no discrete spots along the abdomen. Photo: HJB
Also found in yellow sticky traps have been flies with 3 spots on each wing (below).

Drosophilid fly with 3 wing spots (indicated by blue boxes). Photo: HJB
In addition to flies which may potentially be confused with male SWD, there are also flies which may be difficult to distinguish from female SWD. The most important female feature is the prominent ovipositor (below). The ovipositor can be hard to distinguish when insects are on yellow sticky traps, but can be teased out and still appears different than that of any other female fly.

SWD ovipositor. Fly captured in Edgecombe County, NC. Photo: HJB
Female SWD on yellow sticky trap, ovipositor indicated by blue box. Photo: HJB
Ovipositors of non SWD females are much smaller and lack the dark brown teeth on the anterior margin.

Non SWD females. Note much smaller ovipositors that lack dark marginal teeth (click to enlarge). Photo: HJB

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