Controlling Spotted Wing Drosophila and a Possible Natural Predator to SWD

Berries are my favorite food. I have made it my personal mission to grow every berry suitable for our growing zone. All was going well until 2012 - that is the first year the Spotted Wing Drosophila (hear on out referred to as SWD) showed up in my garden.
Just picked raspberries - this is the daily haul in the early part of September. Believe it or not, the berries get more plentiful toward the end of September.
I was devastated. I battled SWD each and every year. I followed all the hygiene guidelines, I picked the berries daily, and I even tried some organic pesticides. Nothing stopped them. I felt like such a failure. I almost quit gardening for good.

I spent countless hours deciphering the SWD life cycle, how they react to different temperatures, which pesticides work and why, and how they survive the winter.

I came up with plans to swap out all of my berry varieties to only grow those maturing when SWD is at it's lowest. This works for some berries but is largely a fool's errand. Red Raspberries overlap the SWD in all cases - except possibly the early floricane berries like Prelude, Reveille and Boyne.  In our area, they seem to ripen in late June, early July - just when SWD is starting to get going.

I am still contemplating whether I can swap my fall bearing red raspberries to one of the early summer berries or not.

But from where I stand, I think the SWD are here to stay. Just like the coddling moth - they are going to haunt berry growers forever.... But all may not be lost.

I have come up with a few SWD observations that I think are helpful to solving the overall problem and have discovered some solutions that have been working for my family.
First off - a possible solution has landed in my garden. 2015 is the first year I have seen the bald faced hornet. They are "only" in my garden area and no where else on my property. I have never seen them before and had to google "black and white bee" and search through the images to identify it.

I have tons of them and they love my raspberry canes. They have been spotted inside squash flowers and around my tomatoes, but 99% of them are on the raspberries. What are they doing there?

Pollinating? Sure. Eating bugs, maybe? Actually, wasps (and hornets) do not "eat" bugs. They kill them, mash them up in their mouths and feed them to their larvae. Sounds good to me. Could they be killing the SWD?

It's too early to know for sure, but here are the facts in my garden.
1. Bald Faced Hornet is visiting my garden in large numbers - hanging out in the raspberry area the majority of the time.
2. My garden borders a large oak/maple/basswood forest. They may have a hive in the trees - I will be checking for it after leaves drop. (Update - I found their nest in a neighbor's tree)
3. They are buzzing around flowers.
4. They are biting holes in the bottom of my raspberries.
5. SWD is present (I see way too many adults!!!!) and I have had fewer worm issues in the berries themselves.

This is what the bald faced hornet is doing to my raspberries:
A look from inside:
For reference, this is what the bottom of "uneaten" berries look like.
Wow - those are "hairy" looking.
When I find SWD in my berries, the larva are usually in the bottom area of the berry - squirming and ruining everything. Could the bald faced hornet be eating them out of the bottoms?

I have experience with wasps eating my raspberries, and every fall yellow jackets come to feast. They usually hunker down in a berry and eat it until it's almost gone. They seem to "freeze" inside the berry and eat themselves to death or eat themselves until they can barely waddle home. Some are there for days - working on the same berry. I tolerate them because they seem to mostly finish a berry and I can share with pests that finish their share and don't just muck it up for the rest of us. Maybe the bald face hornet is just greedy and wasteful like most other pests. But maybe not. It sounds like a great research project for a budding entomologist or horticulturist. Go ahead and take this idea for your thesis, I'm all good with it. If you find the answer - please let me know!

Here's a shot of a "regular" wasp eating a raspberry. These come out mid-late September and stick with one berry until it's gone - mostly.
It should also be noted that I have seen dragonflies eat mosquitoes and fruit flies right out of the air. Some years we have a ton of dragonflies and the SWD pressure does seem to be lessened, but dragonflies come and go - in some cyclical pattern unknown to me. I also have tree frogs sitting on my raspberry leaves. I have no idea how they got up there or what they are choosing to eat - but I'm hoping they get their fair share of SWD.

In other SWD developments, I have noticed that all the berries in the nature preserve (acres of parkland surround my home) are infested with SWD. I also learned that SWD is most likely unable to survive our zone 4 winters. And I learned that it can fly 6.5 miles per day. It can also hang out in the rain with no issues.  What does it all mean? It means that even with the best sanitation and practices, SWD will be in my garden every year. If it overwinters in the wild areas, it will fly in when my berries are ready. If it does not survive our winters at all, it will slowly make the trek up from the south as the weather warms - or it will hitch a ride on produce coming from these other areas.

SWD is here to stay - like the coddling moth and other pests that attack even in the best of systems. At first this news made me really sad. But then I came to terms with it. Knowing that SWD is always going to be a pest, I either have to stop growing berries, keep fighting to find a way to successfully kill all that enter my garden space, or learn to live with them.

I'm choosing options 2 and 3. I'm not going to spray pesticides anymore. For the record, I've tried permethrin and spinosad with ho-hum results. I have a sprayer and everything. I spray in the evening to protect the bees and when SWD are active, but the SWD are always right back on the bushes the next day.

I am going to experiment with bait/pesticide/traps. It might be a waste of time, but I'm willing to give it a couple tries.

The biggest development in my battle with SWD is the fact that I've decided to just close my eyes and eat them.

I hate what they do to the berries. They make them squirmy and ishy looking. But even with SWD swimming around inside, the berries still taste good. Yes, I know from experience.

Here's my current regime - and it's working quite well.  I pick the berries every day. EVERY day. I pick them as soon as they are ripe. Not as ripe as I like them, but as soon as they are even sort of ripe.

I check over the patch twice to be sure I hadn't missed any. I then take the berries in the house and put them right into the refrigerator. The development of any eggs and existing larva are suspended by cold. Then I eat them. End of story.

If I had apple trees, I would not tolerate the coddling moth. I wouldn't just "eat them" but that's because sprays (even organic sprays) work on the coddling moth -at least mostly. Nothing seems to work on SWD.

I would prefer to pick more of my berries at the "really ripe" stage, but it's just not going to happen. The bonus to this - you do NOT need pectin when you make jam. I have made many jars of really great raspberry jam with nothing but berries and sugar. Sometimes I add lemon if I am going to can them so that they are the right "acid" for canning. Less ripe berries are higher in pectin. So there is an upside....

I would love to hear any ideas, strategies, or tricks you have learned in dealing with the SWD. If you grow Prelude, Reveille or Boyne and can comment on their ripening dates (and your zone) and whether or not you have escaped SWD, I would love to hear it.

If you've seen the bald faced hornet now that SWD is more entrenched in the environment, please share your experiences. Or if you've noticed any other potential predators. My hope is that this article can become a forum for sharing ideas about the SWD and maybe we can find a solution.


For reference: I am currently growing Bristol black raspberry, Latham and Heritage Red raspberries, 5 varieties of blueberries, red/white/pink currants, honeyberries, 2 varieties of grapes, ground cherries, and 3 varieties of  June-bearing strawberries. I also grow aronia berries, a sour cherry, and am in the process of cultivating wild plum, goumi and goji berries. And tomatoes - tomatoes are technically berries. That's all my gardening space. :(



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Thank you for your comments! I appreciate all your tips, advice, and well wishes!

Angela

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