Insect Outbreak Wreaking Havoc on Trees Amid New Mexico Drought

by Taylor Cunningham

An insect outbreak is further damaging trees in some south central New Mexico as they struggle to survive an ongoing drought.

On Sept. 14, officials with the Cibola National Forest said that tussock moth larvae are feeding on the previous year’s needles of the white fir, Doulas fir, and some ponderosa pine trees and causing them to turn brown.

Because of the drought, the trees are already weak, and more vulnerable to bark beetle attacks that often kill tree tops or entire trees. And the tussocks are making them even more prone to attack.

Last year, bark beetles killed off approximately 67,000 acres of piñon trees because a drought made them more susceptible to attacks, according to John Formby, a forest health specialist with the New Mexico Forestry Division.

“If they have enough moisture then trees can try to defend themselves with resin,” Formby said. “And there’s some secondary components of resin that act as insecticides. If they don’t have enough moisture to produce resin, then they really stand no chance if bark beetles feel like they can attack and kill those trees.” 

The Insect Outbreak is Also Dangerous For Humans

Douglas-Fir tussock moths are native defoliators to the Sandia and Manzano mountain ranges, and they’re highly important to the ecosystem. But, in abundance, the moths are known to do serious damage. Officials sometimes have to kill off populations with chemicals to keep them from destroying wooded areas.

“Trees may recover from early infestations which can look quite dramatic,” Steven Souder, a forest Service entomologist, said in a statement. “However, multiple seasons of repeated defoliation can predispose trees to disease and other insects causing tree mortality.”

To keep the tussock moth situation in check, the Forest Service runs annual aerial surveys each summer and records damage done by the larvae. Trees that survive will begin to produce new shoots that turn bronze instead of gold in the fall. As expected, younger trees tend to have a better chance of survival.

To add to the problem, the insect outbreak is also dangerous to humans as well. The caterpillars are covered in thousands of hairs. And the female hairs can cause an allergic reaction called tussockosis. Female moths, egg masses, and cacoons also cause the reaction. So officials are warning people to stay away from the trees.

If people come in direct skin contact with the insect, or the hair becomes airborne, they may experience symptoms that include watery eyes, itchiness, rashes, runny nose, and sneezing. Serious reactions are uncommon, but they include coughing, shortness of breath, wheezing, chest tightness, and blisters.