Piñons under assault by scale insects
“ONE INTERESTING THING ABOUT OUR PIÑONS,” arborist Tracy Neal said, “is that because it’s so dry here, there are almost no diseases they have to deal with.” But the number of insect pests more than offsets that advantage. Piñon needle scale, the Ips confusus bark beetles, and twig beetles represent a tag team that is threatening residents’ enjoyment of wonderful piñon nuts, firewood, and landscapes.
The big problem currently is scale. “That’s why the trees look so bad right now,” Neal said. “In 2004-2005, I saw piñon needle scale start cranking up. Look for those little critters like black dots on the needles. Scale doesn’t kill the trees outright, but it loves the older needles. You see these trees with only the current growth on the ends of the branches. They’re like giant buildings trying to run on a fewsolar panels: there’s not enough energy to power the tree. That sets them up for bark beetle attack.”
Neal, who is also a member of the Municipal Tree Board, witnessed the first piñon trees going down from Ips in 2013, after a drought that started in 2010. But the big dieoff in memory came during the first two or three years of this millennium.
“I was doing meditation at that time, wondering about the significance of all the piñons going down, and the sense I got was that they’re the canaries in the coal mine around here. They were yelling, ‘ Things are getting out of balance!’”
He referred to photographs of Santa Fe in the 1800s, when no piñons are visible in the hills around Santa Fe. “When they came back, they overpopulated. When there are abnormally dense stands of piñon and we’re in a drought, there’s not enough soil moisture to support that many trees. The bark beetles were just coming in as scavengers.”
As if the endemic pests aren’t enough, exotic members of the insect world are becoming more of a threat, because of climate change and international trade, Neal said. “The emerald ash borer from China is on its way south from Colorado, probably in firewood; and the European elm scale that used to just attack the American elms is nowmoving to Siberian elms. Things are radically changing.”
He added that a species of borer insect is killing honey locust trees. And arborist Jeff Clark, the landscape supervisor at St. John’s College, said aspens on the campus are also declining— and those are irrigated trees.
Clark suspects that rising temperatures may be at least as important as reduced precipitation. “That allows more insects to survive the winter, and this last one we had was bothwarmand dry. Our native vegetation knows how to live in our native climate and if that changes, you’ve got a big problem.”
We visited a bare-looking, scale-infected piñon right next to Peterson Student Center that is routinely watered, and Clark expressed doubts that it will be alive next year. “I started seeing piñon scale at least fifteen years before the last beetle outbreak, and it was rare. But the last five years, it’s been outrageous. These tiny insects feed on the oldest needles, which die and drop off. This tree is down to just the current season’s growth on the ends of the branches. Once it’s at this point, there’s nothing you can do.
“Drought affects older trees first, because they have a lot more to support,” Clark said. “Bark beetles thin out the forest. When I first saw these in the 1970s, they would have one generation of offspring a year, then you’d be okay. But the infestation we had in the early 2000s was something we’ve never seen. In some places, we had 12 generations in one year. Nobody had ever heard of that. And I’mwondering if scale is the same way.”
How exactly do we read the landscape, in terms of moisture and temperature, to understand why scale is such a problem in the current drought where before it was Ips? Where are the bark beetles? “Most of the ones I’ve seen recently are only in firewood from somewhere else,” Clark said.
Joanna Prukop was cabinet secretary of the Energy, Minerals & Natural Resources Department during the early-2000s Ips outbreak. “We lost maybe 800,000 piñons in north-central New Mexico,” she said. A former division director in the New Mexico Department of Game & Fish and now board chair of the Santa Fe Conservation Trust, Prukop recalled that by the time extensive beetle damage was evident, the insects had already been at work for two or three years.
“The Santa Fe Conservation Trust does have a couple of very active land managers who already have conservation easements on their land and they’re trying to stay ahead of some of these issues and probably will have to do some landscape management.”
What will that involve? “If you see dead and dying trees,” she responded, “they should be cut out and thewood has to be burned or put inside plastic so the beetles get cooked.”
Right now, the piñon-needle scale insects are weakening a great number of local trees, and Tracy Neal worries that Ips will be next. “This last winter was so warm and dry, we’re setting up for another invasion.”
Above, scale-infested piñons near Santa Fe Preparatory School. Left, a closeup of scale bugs on a branch at St. John’s College