Meet three beetles killing New Mexico trees and one moth making trees bare

Bark beetles are important for New Mexico’s forest ecosystems. They usually attack stressed trees, which are then replaced by younger, stronger trees. Defoliators are insects that eat tree needles or leaves, making them bare of foliage. Defoliated trees can return to normal in spring, but severely defoliated trees might become subject to a bark beetle attack.

The western spruce budworm was the most widespread defoliator in New Mexico forests in 2024, active in 249,000 acres of forest. Here are some of the other busy bugs responsible for tree mortality and defoliation.

1. Ponderosa Pine Bark BeetleLike other bark beetles, ponderosa pine bark beetles eat phloem, a vascular tissue in plants, which moves food made in leaves to other parts of the plant. There are five species considered ponderosa pine bark beetles: southwestern pine beetle, roundheaded pine beetle, red turpentine beetle, pine engraver and the sixspined ips. The red turpentine beetle is the largest bark beetle in North America, according to a ponderosa pine bark beetle guide from the New Mexico Forestry Division.

In 2024, ponderosa pine deaths caused by bark beetles jumped from 5,500 acres of forest to 32,000 acres, according to the 2024 New Mexico Forest Health Conditions report.

2. Douglas-fir Tussock Moth

In its adult form, this moth is a nondescript gray or brown, but as a caterpillar, it has distinctive white tufts and bright red spots. The caterpillar was responsible for defoliating — removing leaves from trees — 18,000 acres of mixed conifer forests in New Mexico last year, according to the report. That’s a significant jump from 2023, when it defoliated 2,600 acres.

3. Mixed Conifer Bark BeetlesThere are two mixed conifer bark beetles in New Mexico: the Douglas-fir beetle and the fir engraver. These beetles were busy in 2024, causing tree mortality in New Mexico, especially near 2022 wildfire burn scars. The Douglas-fir beetles contributed to tree mortality on 13,500 acres in New Mexico, according to the report.

4. Spruce Beetle

In 2024, these dark brown or black beetles were connected to Engelmann spruce deaths for 9,900 acres of high elevation forests in New Mexico. That’s a 20% decrease from 2023. Many of those tree deaths were on national forest land in the Santa Fe and Carson forests.

Spruce beetles prefer to live in high-elevation, large-diameter stands of Engelmann spruce, according to the report. The number of spruce stands has gone down significantly because of spruce beetle attacks and wildfires.