Spotted wing drosophila parasite found on east coast

There were lots of tiny parasitic wasps on my figs this year, something I had never seen before. After some research and looking at them under a microscope, I was fairly confident they were Leptopilina japonica, but to be sure I put some overripe figs in jars to see if they hatched out. There was a hatch of SWD, D. melanogaster and African Fig Fly first, and now several weeks later I see dozens of these wasps in the jars.

Leptopilina japonica has been in the PNW for several years now, along with another parasitic wasp, Ganaspis brasiliensis (which I did not see, but only looked at a few wasps under the scope). But I have not found reports from anywhere else in the US yet.

It isn’t clear yet how much of an impact natural parasites of SWD will have on the problem. The thinking though is that they will be the biggest help controlling SWD in non crop areas, because the pesticides used to control SWD also kill the wasps.

It also isn’t known how either of these new wasps will survive in cold climates. I feel like there were enough of them in the summer that they probably had been here in the spring already, but last winter was extremely mild so that doesn’t seem like a guarantee. G brasiliensis was just approved for rearing and release in the US, but I believe L japonica has not been approved yet.

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Very cool! This is the sort of news we can use. Thanks for sharing.

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Thanks for being so observant and for sharing this important discovery with us, Brent. It gives us some hope. AFFs and SWDs wreaked unprecedented destruction here in September and October; they even attacked dropping native persimmons—which is something I’ve not seen before. Regular applications of spinosad on figs were, at best, only mildly helpful—not to mention expensive. Hope I didn’t kill any parasitoids. I will definitely keep a lookout for them next year.

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Brent, you are a true fig pioneer! Thanks for all your observations. This is the kind of news I was looking for as we have neighbors with untended trees that drop fruit right before my figs started to ripen. The SWD were brewing up, and just waiting for my figs. I can only do so much about SWD in my yard, but nothing much when they’re on someone else’s property.

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Fortunately, I don’t have that problem! I do however notice they tend to build up in my compost bin by mid fall. I’m trying to come up with a mitigation plan before I start to have a lot of fruits producing in the next few years. Maybe putting BTI pellets in periodically would do the trick…

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I am not aware of any SWDs in my 3-acre orchard, but glad to hear there is a natural control on the horizon. I have been using hummingbirds to help eradicate any that may move in, but it is very time-consuming maintaining the feeders.

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What details in the microscope view matched the characteristics of L. japonica?
In the first image, the antenna looks too short.
2nd image looks more promising, antennae >= 2/3 of body length.
Do your wasps have caramel-colored legs, typical of L. japonica?

A and B were apparent to me, C was difficult to make out. The legs were brownish.

The first pic I probably squished him a little getting on my finger. I did notice that the antennae of the freshly hatched ones look much longer. Would their age have anything to do with that?

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No, there is no growth of the adult wasp after emergence.

L. japonica has distinctive orange-ish legs that are much lighter than the body color, like the thumbnail image shows next to your above link.

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I got a pretty good picture of a dried one I collected in the summer. It is just a edit: 20-60x handheld, very frustrating to position the camera…

The freshly hatched ones look strikingly similar to this picture taken by an entomologist in BC, with antennae 1.5x their body length and a more humped abdomen.


http://www.waspweb.org/Cynipoidea/Figitidae/Eucoilinae/Leptopilina/Leptopilina_japonica.htm

I seperate a few out and put them in the freezer and will try to get a picture with some natural sunlight for more detail.

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Maybe you can send a specimen off to the folks studying SWD parasitic wasps. That would probably give you an ID confirmation. Your fig orchard would turn into a research plot at that point!

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I was thinking of sending some pictures to the entomologist in BC since he has firsthand experience with them.

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…and there are the orange legs. These were not apparent on the earlier images.

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Looks like the ones with long antennae are the males. I noticed a few with short antennae and stockier bodies yesterday, was starting to think there were 2 different species. But today i saw them mating. The females must emerge a little bit later.

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You might try parasitic nematodes. The Green Spot in Nottingham,NH may still be around, and still sell them. If not, they are available online. These nematodes would attack any larvae living in the soil where they are released. Spinosad is also supposed to be effective in the soil.

When you say they will “attack any larvae”, do you mean SWD, only?
I have a serious problem with several varieties of grasshoppers, and would love to eliminate their larvae. ( I’ve been spraying trees with a garlic/hot pepper solution.)
But, I don’t want to harm the firefly larvae, or any beneficial insects I don’t know about.

@VickyNY , I don’t want to sidetrack this thread too much, but you might be interested in something like this: Grasshopper Control in Gardens and Small Acreages - 5.536 - Extension

Here’s the part I thought would interest you:

" Nosema locustae Baits

Baits containing the protozoan Nosema locustae is a biological control option that may be considered for treating grasshopper breeding sites. This is sold under the trade names NOLO Bait or Semaspore and can produce infection of many species of grasshoppers. Because it is selective in effects, only affecting grasshoppers, its use is sometimes considered desirable.

There are some limitations to Nosema locustae baits. Only young grasshoppers are susceptible, and it can not be used effectively after adult migrations have occurred. It is also fairly slow acting and does not equally infect all grasshopper species. Often it is most effectively used in a long-term grasshopper management program, in combination with other controls.

Nosema locustae baits are also perishable. They are best kept refrigerated before use. Expiration dates are usually printed on packages and should be checked."

Note that I’m not making a recommendation here- I just know that our local county extension agent suggests it from time to time and it made me think.

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Nosema is generally considered to be a joke among the grasshopper experts but maybe it would work on a very small scale. Don Roberts at Utah State made it his life’s work later in life to find native pathogens that would actually have some sort of effect on grasshoppers. Metarhizium is the fungal infection that grasshoppers get. He was looking for the perfect one. I think there might have been something found in Australia, but they were prohibited from bringing them in. So, he had people sending soil samples from all over the US anytime they might find a sick/dead grasshoppers. He never found anything in the US. Generally, grasshoppers in their native areas can self regulate their body temps and raise their temps to such a degree that it kills any infection including the Metarhizium. That doesn’t work for the grasshoppers if the weather turns cool/wet…but then the natural diseases hopefully help out in that case (if it can turn cool and wet when the hoppers are young enough).

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That’s interesting. Thanks for the information.

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Hi Vicky,
There are different species sold that have somewhat different preferences for where in the soil they are active, and generally they seem to be sold as mixed species to be a general treatment. But they are pretty expensive to use over a large enough area to control something like grasshoppers. Also, they probably would attack other larvae. They seem to be most useful in small areas and places like greenhouses. Sorry, I know grasshoppers can be very problematic.