Southwestern Region

Southwestern Region
333 Broadway SE [map]
Albuquerque, NM 87102
(505) 842-3292
TTY: (505) 842-3198

Natural Resources

FOREST HEALTH: Bark Beetle Outbreak

Several years of drought and high tree densities combined to allow pine bark beetle populations to reach outbreak levels during 2002 - 2004, killing millions of piñon and ponderosa pine trees in Arizona and New Mexico. Large areas of mortality, especially around cities of Santa Fe and Flagstaff generated much public concern as many trees died. The areas most affected are those where trees were at the lower end of their elevational range. Data from aerial surveys recorded 2.1 million acres of piñon-juniper woodland and 1.3 million acres of ponderosa pine affected in Arizona and New Mexico during the 2002 - 2004.

These insects are native to the piñon-juniper woodlands and ponderosa pine forests of the Southwest, normally attacking only a small number of diseased or weakened trees. A healthy tree is typically able to defend against a bark beetle attack by pushing the beetles out with sap. The drought has left many trees with little ability to defend against bark beetle attacks. Additionally, the high tree densities of southwestern forests have contributed to weaker trees due to competition for water and resources. The last major outbreak of these bark beetles in the southwest occurred during the 1950’s drought.

The amount of piñon and ponderosa mortality in 2004 was substantially less than in 2003, a result of the combination of slightly greater precipitation and the fact that many of the trees in the most susceptible areas have already been killed. The amount of new mortality in ponderosa pine and piñon-juniper woodlands further decreased in 2005. For current information on bark beetle activity, see our most recent annual conditions report available on the Publications page.

The following factsheet provides a brief overview of the bark beetle outbreak:

• Factsheet on Arizona Bark Beetle Epidemics (PDF, 53 kb)
• Factsheet on New Mexico Bark Beetle Epidemics (PDF, 35 kb)