Spotted Wing Drosophila (SWD) Biocontrol and Integrated Strategies
AKA: vinegar fly, cherry fruit fly, cherry vinegar fly, Drosophila suzukii
Family: Drosophilidae. Subfamily: Drosophilinae. Genus: Drosophila. Tribe: Drosophilini. Author: Matsumura
Attract and Kill Strategy
The SWD is attracted to active yeast, and a fly eating fungus, Beauvaria bassiana, brand name balEnce, has been developed commercially in the US, EPA registered. This is a strain that is specific to flies. It works well against Drosophila. It would be interesting to see if a yeast (live or dried) bait could be made up with the Beauvaria as the active agent in an attract and kill strategy. A spray with the yeast and balEnce could be sprayed in the field on a weekly schedule to suppress the drosophila. Other bait and kill strategies use about 10 gallons spray per acre, with large droplets, widely scattered.
see SWD bait spray page
US EPA registered 70787-2
CA EPA has not yet approved balEnce registration in CA. Ok to use in OR, WA
Sample material is available for researchers to do trials.
balEnce material info
There are also a couple of possibilities for predators on the spotted wing drosophila (SWD) that are commercially available. These are Atheta, a rove beetle, and nematodes that eat fly larvae, Steinernema feltiae. The SWD larvae will sometimes drop to the soil to pupate and be available to the predators or parasites on the soil surface. Fallen fruit also fosters SWD on the soil surface.
beneficial nematode bulletin
These would be experimental for this particular pest. Some studies have been done on Atheta on cabbage maggot, and S. feltiae on various fruit flies, fungus gnats and house flies.
You can grow ground beetles by having a mowed perennial cover crop (ideal) or at least cover crops in the rainy season.
D-Vac Monitoring for low populations
The D-Vac vacuum insect net works very well to sample SWD populations when low. A D-Vac sample will collect flies when none are coming into traps.
Re: SWD baits for monitoring
Following are excerpts from a message to me from Janet Caprile's work (Farm Advisor, Contra Costa & Alameda Counties) about her standard for monitoring SWD in cherries:
Bucket trap (with a white bottom)
1" of apple cider vinegar on the bottom (about 8 oz) - changed weekly
Hung about 4' high in the shade on the NE side of the tree.
If flies and too many other contaminants are getting into the trap so it is hard to see the Drosophilla, then a strip of 1/8" hardware cloth wrapped around the entry will keep many of those out and let the Drosophilla in.
I have been dumping the spent bait and flies into a bucket and carrying it out of the field so that it won't reduce trap catches if they are going to the old mix on the ground.
The nice thing about the apple cider vinegar is that it is clear and it is easy to read the trap in the field - just look for the little guys with the black spots on the wings. The addition of yeast to the vinegar will increase the D.suzukkii counts a bit - but it also doubles the catches for the other D.spp. and attracts more flies and notidid beetles and other contaminants so that it is harder to see the D.suzukii. So - it is not worth the additional attraction. Yeast also makes the liquid cloudy - so you have to strain it in the field and refloat the catch in water - rather than just count and dump. The Baker's yeast (which is what Show and Bolda have been using) is HUGELY attractive for the first couple of days as it is actively fermenting - and then the attractiveness levels off to that of vinegar over the week (in my quick tests). The change in attractiveness makes it too variable to be a reliable indicator of actual populations.
bucket trap like the unitrap bucket trap?
The Unitrap bucket looks like what I'm using - the one with the white bottom makes it easier to see the bugs - but make sure it doesn't have holes in the bottom - some of them do.
I don't think a mass trapping approach will work (it hasn't with our other pest flies) as there is too much other stuff out there to attract them - so you aren't getting a high enough % in the traps. These traps aren't specific to D.suzukii - it is just a general feeding attractant. And the attractiveness changes over time (even with the vinegars I believe) so you would have to continue to change the bait regularly - too labor intensive.
A Comparison of Torula Yeast, Yeast + Sugar + Water and Commercial Filth Fly Mix
Author: Mark Bolda
Thursday November 12 2009
The following is a summary of further comparisons of baiting techniques for the spotted wing drosophila Drosophila suzukii. Previous posts have evaluated the use of various fruit purees and other mixes and these have determined that a mixture of one 2.5 oz packet of yeast + 4 teaspoons sugar + 12 ounces of water distributed in four or five Mason jars were very effective in monitoring and evaluating infestation levels of spotted wing drosophila.
Another test of baits was run last week. Traps (a 500 ml Nalgene bottle with 4 holes in the lid) containing one pellet torula yeast (see photo below) dissolved in 100 ml water, the yeast + water + sugar bait mixture mentioned above and finally a commercial “filth fly mix” called Yellow Muse (AgBio Corporation) allowed to cure for several weeks (the fermentation process of this material may be important) were placed November 3, evaluated November 6 and then again evaluated November 9.
“Females” means that they are vinegar flies without spots on the wings and assumed to be spotted wing drosophila (SWD), while males were readily identifiable with spots on the wings.
From the chart above, it is apparent that the torula yeast is not very attractive to spotted wing drosophila, while yeast + sugar + water continues to be, along with well cured Yellow Muse filth fly mix, the most useful.
end of blog quote
Yellow Muse filth fly mix is available from Rincon-Vitova under the name of No-Gag-Me fly bait.
The live yeast bait looks most promising as a readily made, inexpensive, bait that is very attractive for 3-4 days. Adding more yeast and sugar as a humectant (drawing moisture) and food source for the live yeast, should make the mix last longer in the field.
I look forward to working with you in some way to see if there is some way to control this pest economically and ecologically.
Ron Whitehurst, PCA
Rincon-Vitova Insectaries, Inc.