It’s small, slow and European. And, it’s one of the newest threats to the forests of the Wasatch Mountains.

No, it’s not northern Utah’s booming population. It’s the balsam woolly adelgid.

Contrary to what its name may suggest, the tiny, almost invisible, insect is not woolly nor cute. Adults measure a mere millimeter long, and their name comes from the white, woolly-waxy shells they produce to protect the hundreds of amber colored eggs they lay. That fuzz is their most obvious tell, other than the destruction they leave behind.

Balsam woolly adelgids are now in Utah, and they are spreading. New research from the University of Utah maps their current habitat and the severity of the insects’ damage. It also offers a warning: Climate change and the subsequent warming of the mountains could cause these tiny harbingers of tree sickness and death to thrive.

“Unfortunately,” said Mickey Campbell, a research assistant professor at the University of Utah’s Department of Geography, “the story is not very optimistic when it comes to the potential future effects of balsam woolly adelgid on subalpine fir trees in our region.”

A 100 year journey inland

It took the balsam woolly adelgids decades to slowly creep, or hitch a ride, across forest floors from Northern Europe to the Mountain West. European trees are relatively insensitive to attack from the bugs, according to the U.S. Department of Agriculture. That’s not the case for the “true firs” — or balsam fir trees — that they seek out in the United States.

True firs like the subalpine fir are their favorite source of food. The balsam woolly adelgids began wreaking havoc on forests of them in the Pacific Northwest more than a hundred years ago. And by 2017, they had made their way to Utah, where they were first detected in Farmington Canyon.

When balsam woolly adelgids latch onto a tree, they not only consume its nutrients and liquids but leave behind a toxic saliva injected through their needle-like mouths.

“And that combination of draining the tree of resources and adding its toxic saliva into the mix,” Campbell said, “is what ultimately drives a tree’s health decline.”

The tree’s limbs become swollen, needles turn yellow and red and the crowns die. It can take years before a tree actually dies.

“We’re pretty used to bark beetles, and bark beetles are the type of insects that come and can do damage pretty quickly to a tree,” Campbell said. “Whereas with the adelgid, it’s really a slow and painful death, if you will.”

The insects thrive in Utah’s lower elevation forests where temperatures tend to be slightly warmer and solar radiation exposure is higher. Those are the areas, like the Farmington and American Fork canyons, where Campbell said the “damaging effects are being seen most severely.”

As average temperatures in the Wasatch Mountains rise, however, so may the population of balsam woolly adelgids.

Climate change could expand their habitat

It has now been seven years since researchers detected the first balsam woolly adelgids in Utah. There are plenty of hotspots, like on the east side of Mount Timpanogos.

“It’s really pretty widespread at this point throughout the central and northern Wasatch,” Campbell said, “it’s just a question of degrees of severity at this point.”

That’s why Campbell and other researchers wanted to get a more complete picture of the balsam woolly adelgid’s presence in Utah and create models predicting how much more of the state’s forest could become prime habitat.

Using just temperature data — minimum spring temperature, number of frost free days annually and in spring and the number of freezing days in autumn — researchers were able to explain with 80% accuracy how severe a balsam woolly adelgid infestation might be in a particular area.

“Which was pretty surprising and was really valuable because we have the ability to map these temperature variables everywhere,” he said. That has allowed them not only to map the current balsam woolly adelgid presence, but look into the future.

The insect population isn’t expected to increase much in the higher and cooler Uinta mountain ranges. But that could change if the most severe climate change projections come to fruition.

The trees in the lower Wasatch Mountain range, however, are more at risk.

“The Wasatch is certainly the most exposed to a potential future in which BWA causes widespread damage in subalpine fir forests,” Campbell said.

If the climate continues warming and more forests reach temperatures where the balsam woolly adelgids thrive, it could mean more dead trees. In turn, that means more fuels for forest fires.

At this point, there aren’t any “broad scale, manageable solutions” to the invasive insects. But forest managers have some tools to prepare for and limit the effects of their proliferation, Campbell said. Measures range from ensuring dead trees are removed to promoting the growth of aspen and spruce trees, which are not susceptible to the balsam woolly adelgids. Another type of Utah fir, the white fir, also seems to be resistant to the bugs, Campbell said.

Sure, they may be small and slow. But just like the boats that may have helped them cross the ocean or the animals they clung to on their journey inland, climate change could provide the balsam woolly adelgids new paths in their march toward dominating Utah’s forests.