If you’ve been seeing more poison ivy while out walking or jogging, you aren’t imaging it..
Unfortunately poison ivy is probably becoming more prevalent due to climate change. But maybe not for the reasons you think.
“We’ve had a substantial deterioration of forest species, a number of trees are dying,” said Mark Brand a professor of horticulture at UConn. “Poison ivy can really get trucking along at that point.”
Professor Brand explained that poison ivy is an opportunistic parasite. Ash trees across the state are dying because of the invasive emerald ash borer, an Asian beetle that burrows into ash trees in thick swarms. Other trees, like beech trees, are facing invasive diseases like beach leaf disease, caused by an invasive nematode worm. Spongy moth caterpillars can defoliate and kill many different tree species including oak and chestnuts.
Even trees that aren’t under specific threat from a new pest are at risk. Connecticut has experienced more droughts, more extreme summer storms and worse nor’easters. None of these are particularly good for tree health.
And when you add in suburban-style development which disrupts forested areas, this creates a perfect environment for poison ivy, Brand said.
With more dead trees, disease, and invasive pests, the more opportunity poison ivy has to spread.
“We are going to have species that are going to fade,” said Brand. “There’s going to be a period of transition where other species can fill in the gaps that used to be occupied by ash trees, and in the transition poison ivy has the advantage.”
On top of this, poison ivy has been demonstrated to react positively to higher concentrations of CO2, known to cause of climate change. A six-year study conducted by a Duke University team found that in a forest where researchers increased the ambient CO2 levels artificially, poison ivy thrived, grew faster, and produced more urushiol, poison ivy’s rash-causing chemical.
So, what’s to be done? Well, if you have a forested lot, or are worried about poison ivy, you need to remove it as fast as possible before it takes over trees. Poison ivy only flowers and spreads when it climbs trees, Bond explained.
“Directed sprays with herbicide are going to be the best approach,” said Brand. “You just need to hit the poison ivy as much as possible and not the desirable plants.”
“I think it’s probably just inevitable that we are going to get these extreme situations and events,” said Brand. “The best people can do is try to maintain plant diversity in their landscape… with a diverse mix it’s not going to be a wipeout event for the landscape.”