Researchers at Oregon State University are studying a potentially effective parasitic wasp to help control SWD. The link to the research paper is in the article but I haven’t had time to read it yet. Hopefully one step closer to an effective biocontrol for this pest.
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This is awesome news! I really hope that this turns into something that effectively combats this awful pest. We are not having an issue with SWD, thankfully, but if ever we did, it would be nice to know that there was an effective biological control for them.
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What FarmGirl said. There are toads in the garden here and would like to keep them around. First the BM stink bug and now this. 
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It would be sooo nice to not have to think about eating those little maggots for half the summer.
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I haven’t, and don’t want to spray any of my cane berries. I try to do my best with cultural control practices, and picking the berries every day or every other, day tend to keep most of the berries useful, but I know there are probably eggs in most of them. However if I go away for a weekend or something then all the berries are infested. Another tool in the kit for controlling these things is welcome.
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An older linked article from 2013 says that they were planning a trip to collect Asian wasps that could be released in 3 to 5 years.
https://phys.org/news/2013-04-fruit-damaging-population-northwest-year.html
Six years has gone by, so maybe the Asian wasps didn’t pan out, or possibly the native wasps are deemed to be sufficiently effective without the red tape of introducing non-natives.
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No it’s that this wasp by laying eggs on the outside which causes no resistance to develop in the fruit fly’s immune system. They inferred the only other known predator wasp lays eggs inside the fly, and antibodies develop over time.
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There are some new developments in biocontrol of Spotted Wing Drosophila that may be of interest to current berry and fruit growers. Most of the proposed SWD control strategies (physical, chemical and biological) have focused on reducing the adult population of SWD, with variable success.
A more promising target for SWD biocontrol may be the SWD reproductive cycle, which can be more accessible. In the case of soft berries like raspberries, this cycle is completed in the ground of growing beds. And a beneficial nematode (Steinernema feltiae) that is commercially available has been shown to be effective at parasitizing and killing SWD larvae and pupae in the soil. This potential Sf effectiveness for SWD control has been validated by laboratory and field research with blueberries at MSU: Nematodes vs. SWD - Good Fruit Grower
My 6 year experience with heavily SWD-infested raspberries in western NC has been very positive: Rapid SWD reductions on harvested berries over the first 2 years of Sf nematode applications (2016, 2017). And then no SWD-infested berries detected from 2018 to the first harvests of 2023.
Of course, having a biocontrol method that is more effective than the chemical alternatives would be a real plus for organic berry growers! And an extension to SWD control in hard fruits may also be possible.
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I don’t know about other areas, but here in an urban area adjacent to Vancouver, BC, Canada, we suffered through about three years of increasing populations of SWD; but during the last four years the population has been decreasing significantly. During the last two years I didn’t notice any SWD presence in my raspberries until late in the fall-bearing raspberry crop, and even that was not very damaging. I was netting my cherry trees with floating row covers, but now it’s no longer necessary. I wonder if some natural predator of SWD fruitflies has had an impact on their population, or maybe it’s part of the general decline of insects that’s been reported in recent years. Has anyone else in the Pacific Northwest noticed a decline in SWD numbers?
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Thank you for this interesting account of declining SWD burden on your fruit. I hope that we will get some other reports about natural SWD population declines from PNW, or elsewhere.
One promising candidate for SWD biocontrol is a predatory Asian wasp ( Ganaspis brasiliensis) which parasitizes the adult SWD. This has been recently approved by USDA for US release and looks to be effective in reducing SWD populations.
But what connects this to your experience is that this wasp has recently been wild-collected in both British Columbia (2019) and Washington state (2021). So it could be already naturalized in your area! https://www.growingproduce.com/crop-protection/insect-control/its-a-first-spotted-wing-drosophila-enemy-found-in-u-s/
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I know there is also a predatory wasp that was recently approved for Japanese beetles. Does anyone know where to get any of these predatory wasps? I would absolutely love to release them in my garden!
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If you have the scientific name for this predator wasp you can just search on Amazon to find a commercial source. But if this was only recently USDA/APHIS approved for commercial use, you may need to check with your County Extension for a source.
BTW, I have found Milky Spore - a ground-based bacterial predator that attacks the grubs in the ground - to be an effective Japanese beetle control. It takes 2-3 years to get going and you need to have access to the grassy breeding areas used by the beetles. But once established it should provide long time control. It did for me!
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