Wasp Biocontrol Update 6
Published: 27 June 2016 - by Ronny Groenteman
Adult Sphecophaga. Photo: Bob Brown.
The past few weeks have brought much excitement to the project.
First, if you haven’t seen it yet, do check the nest excavation video that went viral! Bob is in the lead role, in a bee suit. He is also the cameraman, the script writer, the editor and the producer. What an amazing reaction this one generated – Bob made it to global media, including Discovery Channel, Canada who sent a crew to film Bob at work. Not yet known when the Discovery Channel item will be aired.
Together with the Discovery Channel crew, Bob was able to film the mites close up, which led to his discovery of the way the mites interact with the wasps. The first thing to understand in this context is how wasp nests operate like an organism, and how the different casts in the colony function like different organs. The workers are the long arms, venturing out to bring prey, but are unable to digest that pray. The larvae that occupy the cells in the comb are the colony’s stomach: they get fed prey by the workers, digest it, use some for their own growth, and regurgitate the reminder to feed the workers. It turns out that the mites feed on this regurgitated protein, robbing it from the workers.
Remember the mite gut analysis we told you about in update No. 4?
The results came back with no wasp DNA, and in fact with only mite DNA. Now we understand why: the mites feed on food that is well-digested, and any bit of DNA in it is completely broken down by the enzymes in the guts of the wasp larvae. That’s one riddle solved.
To summarise our knowledge we gained in the project to date:
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Where to from here?
We suspect that robbing workers from food is not enough to cause wasp nests to be smaller and workers less aggressive. It is likely that the mites are involved in disease transmission to wasps. This means that in order to test the safety of the mite to honeybees and bumble bees, we would need a complex setup including molecular testing that go beyond our means in the current project. This also means that the mite may be more reasonable to develop as a medium-scale medium-term biocontrol agent, i.e., one that would take some repeated efforts in augmentation. In addition, work to underpin some of the basic science questions about the mites abilities to evade nest hygiene and about their ability to vector diseases to wasps is now incorporated into the Biological Heritage National Science Challenges.
In our project though, we want to make more progress towards a long-term, landscape-scale biocontrol.
In our recent committee meeting we have decided to refocus the project to look for wasp natural enemies that could do that.
We are now working with MPI’s Sustainable Farming Fund to re-define the project for its remaining year-and-a-bit. While we will continue to do a small amount of work on the mite, we will now turn our main efforts to bringing new genetic stock of the parasitoid Sphecophaga to New Zealand. More on that in the next update.
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