Controlled-Release Dispenser and Dry Trap Developments for Drosophila suzukii Detection

Abstract

The spotted wing drosophila (SWD), Drosophila suzukii, is an exotic vinegar fly originating from SouthEast Asia and has invaded many American and European countries. This devastating pest has caused severe damage on soft-skinned fruit crops, which has resulted in large economic losses. Although many D. suzukii detection devices have been developed and used by growers/farmers in orchards, most of them did not meet their expectation. More simple, convenient, and efficient detection tools are still urgently needed so that growers/farmers can make timely management decision. In our previous study a quinary blend, containing acetoin, as a long-range, and ethyl octanoate, as a short-range attractant for SWD, had been identified. In this study, a controlled-release polyethylene dispenser containing five identified attractants: acetoin, ethyl octanoate, ethyl acetate, phenethyl alcohol, and acetic acid, was tested in laboratory conditions for release rates, as well as in a blueberry field and an adjacent wooded area for trapping activity. Release of the most D. suzukii attractants from the polyethylene dispenser was constant. In the laboratory, release rates of ethyl acetate (0.3 g/day over 14 days), phenethyl alcohol (0.0054 g/day over 36 days), and acetic acid (0.13 g/day over 36 days) followed zero order kinetics. Acetoin and ethyl octanoate were blended together and had a varied release rate. In the field, dry and liquid traps baited with the optimized controlled-release dispenser were evaluated and compared with liquid traps baited with apple cider vinegar (ACV). During blueberry harvest season in 2018, the liquid traps containing drowning solution baited with the optimized controlledrelease dispenser caught both male and female D. suzukii 2 weeks earlier and had significantly higher selectivity than that of ACV traps in the field. Additionally, in 2019 field tests, dry traps baited with the controlled-release dispenser demonstrated earlier detection compared to the ACV traps. Due to the simplicity of the dry trap design and easy processing, it has great potential to be an efficient and convenient D. suzukii detection tool for growers/farmers.

Field Evaluation of Different Attractants for Detecting and Monitoring Drosophila suzukii

“…A portion of the improvement in selectivity could be attributed to the fact that the dispenser components within the ChemTica dispenser are contained within bags that are meant to control the components' release rates. Further support for this can be found in Larson et al (2020) where the QB was formulated into polyethylene sachets as a controlled-release dispenser which resulted in the selectivity for this version of the QB to range between 41 and 51%.…”

“…In this study, the selectivity of the Scentry dispenser ranged from 1 to 30%, while the selectivity of the Trécé dispenser ranged from 6 to 13% depending upon the year and location. Poor selectivity (in terms of low value as well as high variability due to regional and temporal placement) and efficacy have repeatedly been cited as barriers to achieving a highly successful SWD dispenser (Basoalto et al, 2013;Iglesias et al, 2014;Feng et al, 2018;Tonina et al, 2018;Larson et al, 2020). Improving the efficacy and selectivity of a dispenser can have several positive effects including reduction in beneficial by-capture, increased ease of identification of the target pest, ability to mass-trap or trap-out the pest, and a reduction in decaying off-target bio-mass which in turn could improve the length of time a dispenser is attractive (Adams et al, 1989;Landolt et al, 2012).…”

“…The preparation of QB dispensers has been previously described in Larson et al (2020). In short, a cotton ball, inserted into a micro-centrifuge tube (1.5 mL Eppendorf micro-centrifuge tube, VWR International, Radnor, PA, United States), had 1 mL AT: EO (1:1) loaded onto it.…”

“…50% (Feng et al, 2018). When formulated this synthetic QB into polyethylene bags as a controlled-release dispenser, a significant reduction in non-target drosophilid captures was observed (Larson et al, 2020). This reduction in non-target drosophilid capture is needed to reduce the time required to identify SWD within the trap, in addition to reducing the chance of misidentification, and ultimately improving sampling efficiency (Kirkpatrick et al, 2017;Cloonan et al, 2019).…”

Tunnel entries and a killing agent uncover the importance of fly retention in Drosophilasuzukii traps

“…Several chemical compounds, attractive to D. suzukii, were recently identified and controlled release dispenser systems were evaluated. [18][19][20][21]42 This would mean the inconvenient weekly changing of the liquid attractant (which also serves as a drowning solution) would no longer be required.…”