With names that sound like they were lifted from a horror novel, different kinds of tiny insects seem to launch a new invasion threatening Santa Fe’s urban forest every year.
It was the airborne and awful ash whitefly two years ago. Then came the dreaded honey locust borer last year. Now, the evil European elm flea weevil is here, eating away at all species of elm trees in Santa Fe. Each one is a type of non-native invasive tree pest that has been identified as new to the area by Victor Lucero, who heads up city government’s Integrated Pest Management program.
In a recent report about “Pests of Concern,” Lucero writes that the weevil larvae “mine and feed inside the leaf tissue,” and adult weevils leave tree leaves with a “shot hole appearance.”
Invasive pests such as these can damage trees in a variety of ways, spread disease and in some cases kill them by choking off their water supply.
Lucero warns that the European elm scale, fruit lecanium scale and the elm leaf beetle are already here, and in large numbers can cause branches to die back and premature leaf senescence, destroying tree canopies.
It’s not just Santa Fe. Insect invasions to ash, elms, oaks and piñon trees in the City Different are no different than what’s happening elsewhere.
“Generally speaking, across the entire country, we’re seeing an invasion of all urban forest species,” says Jennifer Dann, manager of the state’s Urban and Community Forest Program.
And they come from all over the world.
Dann says some bugs cross oceans embedded in wood pallets or in shipping containers, arriving at seaports up and down the continent. They’ll then often hitch rides on trucks, so they invariably pop up along highway corridors.
They sometimes latch on to ornamental trees sold in nurseries or in firewood, leading The Nature Conservancy to create the website dontmovefirewood.org, which implores people to “buy it where you burn it,” to limit the spread of invasive pests.
“Some of them aren’t here yet, but we know they’re coming,” Dann said of the non-native intrusive pests, noting an interstate highway passes right by Santa Fe.
The ‘green menace’
One yet to arrive is the emerald ash borer, which in recent years has turned up six hours up the interstate in Boulder County in Colorado and next door in Texas.
The green invertebrate is the worst nightmare for city Parks Director Richard Thompson.
“It keeps me up at night,” he says of his fear of the bug.
Thompson says city workers are bound by ordinance to follow an Integrated Pest Management strategy that allows for pesticide use, though that’s a last resort.
But there appears to be no stopping the emerald ash borer, or EAB for short. He says trees infested by the bug have a 90 percent fatality rate. Once a tree is infested, it may be dead in two to four years.
Tom Zegler, the Forestry Division’s forest health program manager, says that when the emerald ash borer arrives – and it will arrive – it will bring devastation.
“We expect it will be the most damaging invasive pest since the chestnut blight in the early 1900s,” he said of the fungal infection believed to have been transported to this continent from Japan in nursery stock and that nearly wiped out the once plentiful American Chestnut tree.
Zegler says little can be done about the EAB except “try to slow its spread.”
“This insect has already devastated the native American ash population in the Northeast,” he said. “What it does is disrupt the flow of water through trees. There’s no genetic resistance to it in ash trees, so basically as soon as it arrives, it will kill any ash tree in our urban forest.”
The EAB, native to northeast Asia, is believed to have turned up first in North America in southeastern Michigan in 2002, probably on ash wood pallets or wood packaging material. It has since infested millions of trees in 27 states and is estimated to have cost billions of dollars to treat, remove and replace ash trees.
The “green menace,” as it has been called, was first confirmed in Boulder in 2013. Officials there are worried because there are about 98,000 ash trees in the city and roughly 1.45 million in the Denver metropolitan area.
Zegler says there are treatments to try to thwart the threat, but they’re expensive and probably impractical. There are too many trees in the forest, but it can be done on a more individualized basis.
Websites advertise various insecticides to fight EAB.
“With any dead or dying ash trees, it’s very important that they are detected early and contained,” Zegler said. “You can’t do it in the forest, but it’s something homeowners can do.”
In the meantime, “What we recommend is that city planners and urban foresters plant a variety of trees to replace ash,” Zegler said.
Because existing ash trees may be good only for firewood before too long.
“It’s only a matter of time,” Zegler said of the EAB’s arrival. “It’s already on our doorstep.”
Keeping them in check
Entomologist Tom Coleman of the U.S. Forest Service fears the Emerald Ash Borer too.
“Early detection of these exotic threats is crucial for implementing management options,” Coleman said. “We are also running survey traps in coordination with this monitoring effort at the Albuquerque and Santa Fe botanical gardens.”
Coleman said USFS’s Forest Health Protection monitors urban forest health in several New Mexico cities because the pests are most commonly first detected in urban areas. The USDA’s Animal and Plant Health Inspection Service has also set up traps to detect the presence of the EAB throughout the state.
Coleman said they are also monitoring invasive bark beetles and wood borers at the botanical gardens.
“We are generally more concerned about bark beetles and wood borers because trees are less tolerant to this type of injury, whereas trees can better tolerate injury from leaf-feeding insects. The diversity of trees found at the gardens makes them a great place to survey,” he said.
Coleman warns of another exotic pest probably coming to New Mexico, the European gypsy moth, which could someday threaten the stands of aspen in the mountains overlooking Santa Fe.
“The caterpillar can feed on hundreds of tree species, but prefers to eat oaks and aspen,” he said. “It’s currently found in the northeastern part of the U.S., but moths are frequently collected in other parts of the country. Repeated bouts of severe defoliation can lead to tree mortality or predispose them to attack by other insects.”
Coleman says that the EAB and European gypsy moth are two of the most prominent exotic insects because they travel well.
“The movement of firewood has been attributed to the spread of the emerald ash borer in the U.S., whereas the European gypsy moth will lay egg masses on vehicles, lawn furniture and outdoor tools, which are then moved to other regions of the country,” he said. “We stress that people buy local firewood and to not move firewood long distances.”
Zegler of State Forestry has the same message … because they’re coming.
“What I tell people is the emerald ash borer is just one truckload of firewood away,” he said.