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A bizarre fungus is threatening two emerging cicada broods


This spring, two broods of periodical cicadas will emerge in parts of the South and the Midwest. Soon, male cicadas will congregate in the treetops and sing love songs very loudly to females they're hoping to woo. The co-emergence of these two broods has not happened since Thomas Jefferson was president. It's a huge moment for scientists devoted to the mysteries of periodical cicadas and also for those who study fungus, including Matt Kasson. He's an associate professor of forest pathology and mycology at West Virginia University. Hi, Matt.


SUMMERS: OK, Matt, so tell us - why are we talking about fungus during a periodical cicada emergence?

KASSON: Periodical cicadas are a spectacular thing to witness. Like many animals, they, too, are susceptible to diseases. And one of those diseases they get is a fungal infection by a fungus called Massospora cicadina. It's a really unique fungus that does something called active-host transmission. It keeps the cicada flying around, even though it's erupted out of the backside of the cicada. A third of its body has been replaced by fungal tissue. This is the puppeteer - the fungus - pulling the strings on its unsuspecting host. It's keeping the host active to attempt to mate to spread the spores.

It's also causing a type of behavioral modification we call hypersexualization so that males, for example, that are infected with the fungus, in addition to trying to mate with females, will pretend to be females to mate with males. And this, again, is a strategy by the fungus to maximize dispersal.

SUMMERS: One of the big questions I have is whether perhaps this could kill off an entire brood or if it could spread to other species.

KASSON: That's a really good question. There are seven known species of Magicicada that make up the periodical cicadas. And all of them are susceptible to this fungus, yet the incidence of infection is pretty low across the landscape - maybe below 5%. We've encountered some areas where it's as high as 20- to 30%. So why is it high in some areas and low in the others? That's what we're trying to understand. With climate change and landscape fragmentation, all these things cumulatively could tip the scales against cicadas to really impact a specific brood.

SUMMERS: The co-emergence of these two broods is something that so many people are looking forward to who just really love cicadas. But for people like you - and you've been studying this fungus, we should note, for almost a decade now - it's also an incredible moment. So what is on the agenda for you? Where are you going to be searching for this fungus?

KASSON: A lot of the work that we've done over the last eight years has really focused on the 17-year cicadas. So that's one of our focal points - to get more infected cicadas from the 13-year population. But also go into those areas where the 13- and 17-year broods overlap. And that's, you know, south of Chicago in Illinois, and that's an area that we're looking to target.

One of the surprising things that we discovered over the last eight years is that this fungus that infects periodical cicadas is currently the largest known fungal genome within the whole entire kingdom of fungi. So even though this is kind of an oddball fungus that was kind of a mycological oddity for 100 years - and really until my lab started investigating it - we're finding out we can learn more about fungi in general from studying this delicate co-evolutionary relationship between this very specialized fungus and its cicada host.

SUMMERS: Matt Kasson is an associate professor of forest pathology and mycology at West Virginia University. Matt, Thank you.

KASSON: Thank you so much. Transcript provided by NPR, Copyright NPR.

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Kathryn Fink
Kathryn Fink is a producer with NPR's All Things Considered.
Juana Summers is a political correspondent for NPR covering race, justice and politics. She has covered politics since 2010 for publications including Politico, CNN and The Associated Press. She got her start in public radio at KBIA in Columbia, Mo., and also previously covered Congress for NPR.