Poison Ivy: Seeds of Destruction

May 27, 2014

Just as the season for getting outdoors gets into full swing, so does a noxious weed that can take the fun out of summer outings.

Poison Ivy, which causes an itchy rash in eighty per cent of people who come in contact with it, is on the rise in the US, fueled by rising C-O2 levels.

But scientists at Virginia Tech have found that the weed contains the seeds of its own destruction –a kind of poison pill could be used to control the plant in the landscape.


Almost everyone has a poison ivy story, even plant biologist John Jelesko. “I had a giant oak tree that fell down in my back yard. I was out cutting down limbs with a chain saw.”

Jelesko knew enough to avoid touching the poison ivy vine growing on the downed tree, but he didn’t realize the chainsaw’s cord picked up some of the oil that causes the itch. When he wrapped it up on his forearm to put it away, he was exposed.

“Next day I started showing symptoms and I never had poison ivy before so I thought, hey e let’s see where this goes.”

And this is the first way the poison ivy plant may have sown the seeds of its own destruction

“And for the next 16 days I developed a very severe, itchy rash and actually sleepless nights.  I started researching what was known about poison ivy and the chemical has been known since the 1950s but exactly what that chemical was doing in the natural environment and how its manufactured in the plant, no one has investigated this.”

Keep a scientist up all night scratching and he may come up with a plan.  Jelesko tried to grow sterile poison ivy plants in the lab. But each time the plants came down with a fungus that eventually killed them.  It wasn’t what he was looking for, but as they say, chance favors the prepared mind so he decided to study the fungus.

“The fungus was coming from the surface of the seeds and we still don u stand what its role is but I what I realized quickly is that I’m not an expert in fungal pathologies.”

 But a colleague at Virginia Tech, Matt Kasson, is. They isolated the fungus, looked at its structure, its spores, their growth habits and DNA.  

"But you know, the biggest question was, is it pathogenic on poison ivy. Sure we were isolating it from these seedlings, but the question is, if we took it and re-infected healthy poison ivy seedlings, would it cause disease and certainly we answered that within a few weeks.  The answer was yes. It does in fact cause disease on poison ivy resulting in mortality of all inoculated poison ivy plants.”

Of course that raised more questions, like what is poison ivy doing with a fungus that kills off some of its own offspring?

“Ecology is very non linear and what we think may be happening is that seeds that fall directly on to the ground would be very crowded and by harboring a pathogen that would kill those seedlings would decrease competition.

Humans are the only species on the planet that gets a rash from the oil in poison ivy. Many animals eat it.  

"Birds eat the seeds and much of the fungus on the seeds gets stripped off as it goes thru the bird’s gut so this may be one way of nature selecting seeds that are transported seeds to a faraway place increasing that increases the invasion of the plant.”

In nature, the fungus doesn’t exist in high enough levels on the seeds to kill all their sister seedlings so in the lab, Jelesko and Kasson used higher concentrations, which did the trick.

“I do think if he can get past the hurdle of getting it into the environment and getting mature plants to succumb, this has some fantastic applications that a lot of people would be excited about," says Tom Mitchell, a fungal biologist at Ohio State University

“To kill poison ivy, on thing people us is chemicals, but the chemicals they use tend to be broad spectrum chemicals so you can’t really go into a forest and start spraying everywhere for poison ivy without affecting maybe native species as well. so one thing about this it might be very specific to poison ivy.

Early studies by Jelesko and Kasson suggest the fungus suggest that it is, and in fact, poison is known to compete out and kill other plants in the landscape, a habit that is expected to continue as CO2 levels in the atmosphere rise, causing it to flourish.

Jelesko and Kasson are working on getting the fungus into granular form so it could be applied to plants the way fertilizer is spread.  The university has applied for a patent, but the key remains getting a commercial developer to see the potential financial reward of bringing it to market.

Professor Jelesko and Kassan’s paper on this natural way to control poison ivy will be published in the July issue of the journal “Plant Disease.”