Spotted Wing Drosophila (SWD) Flights Increase

July 18, 2019

Bill Hutchison, Eric Burkness, Anh Tran, Dominique Ebbenga & Suzanne Wold-Burkness
MN Extension IPM Program, Dept. of Entomology, University of Minnesota, St. Paul campus 

As noted previously, our earliest SWD trap catch dates this year occurred with single adult flies caught in forest edge locations adjacent to crops; the earliest catch was May 23rd at Hastings. The traps in our network are effective at catching both male and female flies (Fig. 1).  Since July 8th and during the past week, SWD numbers for traps located in berry crops (mostly blueberry, summer raspberry) increased substantially – up to 191 and 176/wk at Forest Lake and the HRC-Arboretum, respectively. One exception to this is the Hastings site, where only wine grapes are grown; berries are still very small and green (not attractive to SWD).

swd male SWD female
Figure 1. Spotted wing drosophila male (left), with characteristic spots on the wings, and female (right), with serrated ovipositor (egg-lay device). Photo:  Sheila Fitzpatrick, Agriculture & Agri-Food Canada, Pacific Agri-Food Research Center, Agassiz).

The following Table summarizes the average weekly trap catch for each of our locations in the SWD trapping network, MN.

Table

swd trap

Figure. 2. Scentry Trap for Monitoring SWD adults near black raspberry, southeastern MN (2018); note small SWD adults on outside of trap, waiting to enter via small 1/8” size circular holes. Recent research (Michigan State) has also shown the red color is attractive to SWD. Photo: S. Wold-Burkness.

Traps are checked on Mondays, with the SWD trap page usually updated by Wednesday afternoon each week. To stay up to date on the SWD situation, view the complete SWD Trap Network data at: https://www.fruitedge.umn.edu/swdtrap . The trap catch network is based on our use of the Scentry Trap design (Fig. 2) and 4-component lure; data are summarized on Fruitedge by date and berry crop. 

Spotted Wing Drosophila Traps on Your Farm

Although our Metro Area SWD Network provides one indicator of annual pest pressure, it cannot fully reflect the SWD pressure, or onset of SWD activity, that you experience on your farm. It is therefore best to make, or purchase two or more SWD traps for your farm, to have the best information about SWD infestation potential. We selected the Scentry trap following several years of research, and feedback from other states. The primary advantages include a) an improved 4-component lure (bait) that is more specific to SWD (and therefore fewer non-target flies to sort through), b) the lure lasts up to six weeks (less expense), and c) the catchment area is water-based (with one drop of dish detergent to break surface tension) – vs the use of apple-cider vinegar. One source of SWD traps is the Great Lakes IPM store (MI), on-line: https://www.greatlakesipm.com/

SWD Management Updates for 2019

As per recent years, we annually update the SWD pest profile and management guide for Minnesota. New this year, the SWD guide is also available in Hmong, Spanish and Somali, see: https://www.fruitedge.umn.edu/swdpestprofile