Elm seed bugs latest invasive pest in New Mexico

May 17—New Mexico has had many invaders over the centuries, large, medium and small.

The latest is in the latter group: It's a dark, half-inch-long insect with red markings on its belly, known as the elm seed bug.

It recently emerged in the Santa Fe area after making a long transatlantic journey to the West more than a decade ago.

The bug is not a disease-carrying vector like a mosquito, nor does it damage a home or garden like termites and leaf beetles do. It is more of a nuisance than an environmental or health threat.

The biggest problem is a potential one: If the bugs flourish enough to lay a lot of eggs in an area, they can proliferate and infest a home by the hundreds or even thousands.

The area's widespread growth of Siberian elms — another non-native species — produce bountiful seeds for the pests to feed on, enabling them to thrive. Hence, the bug's name.

Teresa Moore, a Santa Fe resident, said the bugs began appearing in the past year in her home and her neighbors'.

"We do have a lot of elm trees in our neighborhood," Moore said. "I suspect most of them are Siberian elms."

John Formby, an entomologist who consults for state and federal agencies, said he first encountered the bugs several years ago in Algodones, a town between Santa Fe and Albuquerque.

The house was near a forest of Siberian elm trees and had a huge infestation.

"They were just invading her home by the thousands," Formby said.

At the time, he had to research the bug to identify the species and figure out what could be done to combat it, he said.

It has since made its way to both Santa Fe and Albuquerque, with reports growing more frequent of the pests appearing in homes.

The insect will emit a pungent odor if squashed or handled, but it is not a stink bug, which damages plants and crops both by feeding on the leaves and spreading disease. Some stink bugs can spray a noxious chemical several inches.

They grow wings as they mature and become flying insects as adults.

Both the elms and the bugs that eat their seeds have origins in Central Asia. It likely was transported to the U.S. in cargo containers, perhaps as stray infested seeds or in tree-nursery stock, Formby said.

Although the U.S. Department of Agriculture has become more vigilant in its efforts to prevent foreign pests from entering the country, it's virtually impossible to inspect the millions of shipping containers arriving at the nation's ports, he said.

This bug joins the likes of the spongy moth and the spotted lanternfly as intruders that were transported here unintentionally, Formby said.

In the U.S., the elm seed bug was first observed in Idaho in 2012 and has since spread to Utah, Oregon, Washington, Colorado and now New Mexico. Its emergence here is recent enough that almost no literature can be found with information specific to the state.

In Colorado, where the bug is more established, more than 5,600 infestations have been reported in homes, according to the Colorado State University Extension, so it was just a matter of time before this insect migrated south to New Mexico.

The bugs become inactive in the winter, then move to elms in the spring, eating the seeds and laying eggs at the foot of the trees. They seek indoor shelter when the weather become too hot so they tend to invade homes during the summer months, the extension's website says.

One way to keep these bugs out of the home is to seal cracks, crevices and vents and insulate under doors, Formby said.

Moore said totally bug-proofing a house is a challenge. The pests have appeared on indoor sills after slipping under windows that were tightly shut, she said.

Pest-control experts recommend vacuuming bugs that have come into a home. They also advise applying insecticides at exterior spots where the bugs could enter, such as near the outside of doorways and windows.

Moore said her exterminator made similar recommendations about selectively spraying pesticides in a few key areas outside the house. That's about as far as she wants to go, she said, adding she doesn't like those kinds of chemicals.

She tries to clean up elm seeds she spots around her house and the neighborhood as a preventive measure.

One positive side to the bugs coming here is they can curb Siberian elms, which have lacked a natural suppressor since they were brought to the state decades ago, Formby said.

The elms were first introduced to New Mexico in the 19th century but were cultivated in earnest during the 1930s Dust Bowl era as trees that provided shade to the sun-parched ground without requiring much water.

The trees have become troublesome, outcompeting native trees for nutrients and water, enabling them to take over entire stands.

They also are exceedingly resilient — able to regrow quickly after being chopped down — while producing and shedding a massive number of seeds that spread the trees across a large area.

This is where the elm seed bug comes in.

By feasting on the seeds, the bugs slow the elm trees' spread, Formby said.

"So one invasive species may help control another invasive species," he said.