Appearance of Southern pine beetles in New Hampshire connected to climate change, says researcher
There’s a new bug in town.
Researchers at the University of New Hampshire have spotted the southern pine beetle, an insect that feeds on pine trees and can kill them in large numbers, in New Hampshire.
This is the first time the insect has been seen this far north — and Jeff Garnas, an associate professor of forest ecosystem health at UNH, says their presence is connected to climate change.
“What's happening with climate change is that the frequency of very cold nights in the winter is becoming less and less,” he said. “Without those very cold temperatures to kill large proportions of the beetle population, they're able to establish further and further north.”
Southern pine beetles can attack large swaths of pine trees if they’re not managed. Southern pine beetle outbreaks have caused almost $4 billion in damage since 1973 in the United States, according to the Forest Service. In the largest recorded outbreak, between 1999 and 2003, the insects impacted more than a million acres of land across seven states.
Caroline Kanaskie, a Ph.D. student working with Garnas, found the beetles in New Hampshire and Maine in November, using pheromone-baited lures and funnel-shaped traps.
The UNH team has only found a few beetles in traps so far. When they’re at a low density, the beetles subsist on trees that are already stressed, like those that have been weakened from something like a lightning strike or another insect attack.
The beetle is typically found in the southern United States and Central America. but the species has been moving north since about 2000. It was first seen outside of its normal range in the New Jersey Pine Barrens, Garnas said. And there, a warm growing season in 2010 expanded the beetle’s range and ability to harm trees.
As winters warm, the beetle has a chance to gain a foothold in places where the cold has previously kept insects away or populations low. And southern pine beetles can do a lot of damage when they’re in large groups.
The beetle’s pheromones allow insects to aggregate in large numbers – tens of thousands of beetles can swarm a single tree, Garnas said.
“The southern pine beetle is one of the few bark beetle species that has truly explosive population dynamics. It's arguably one of the most aggressive tree-killing insects in the country and even the world,” he said.
The insects first tap out the tree’s defense against beetle attack – resin.
“Once the resin is tapped out, the tree is a sitting duck for colonization by these beetles,” Garnas said.
The beetles invade the tree’s phloem and eat the tree. Sometimes, a group of pine beetles can kill a tree within three or four weeks.
But Garnas says he doesn’t think Granite Staters will see healthy trees dying from southern pine beetle damage in the near future. And New Hampshire’s biggest pine species are less susceptible to beetle outbreaks than southern pine species.
“Thankfully, our most widespread species in this region is white pine, and it's at the very least less susceptible to the southern pine beetle. It can be attacked, but it doesn't seem to be a great host for the beetle,” Garnas said.
White pine is a soft pine, and the southern pine beetle seems to have more of a taste for hard pine species, Garnas said.
Some of the beetles that Kanaskie discovered were in pitch pine barrens in Ossipee. Pitch pine seems to be where the beetles congregate outside of their southern range – and the ecosystem of a pitch pine barren includes unique vegetation and endangered insects, Garnas said.
“It's quite an important ecosystem to protect from a conservation perspective,” he said.
The other big threat would be if the beetles adapted to prey on white pine – but that doesn’t seem to be happening right now, Garnas said.
But Garnas says in 10 or 20 years, it’s possible the beetles could be causing damage.
Aside from the potential damage southern pine beetles could do, Garnas says he’s looking to the beetle as a bellwether for other species moving north as temperatures warm.
“Some mosquitoes and ticks that are disease vectors are also moving north,” Garnas said. “I suspect that as temperatures continue to warm specifically in winter, we're going to see the movement of species more broadly that can really change some of our ecosystems and interact with human health and well-being in some very important ways.”
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