Alamosa District

Insects in the San Luis Valley

Insects have always been a natural part of the forest but we are experiencing outbreaks on a larger scale in recent years due to drought and other forest health issues. Drought stresses on trees making them more susceptible to bark beetles. Other factors that stress trees are overly dense stands, construction disturbance and even over-watering.

In the summer (June-August), bark beetles fly and seek out live green trees to bore into. They over-winter in these trees; their eggs develop into beetles and emerge the following summer, and the process begins again. These trees are called 'Brood Trees.'

The population of the piñon ips beetle (Ips confuses) has increased in the valley. Ips is a common group of bark beetles that infests pine and spruce trees. Other varieties of bark beetles infest and kill trees as well.

Mountain Pine Beetle

Mountain Pine Beetle – Saguache County was listed as one of the areas with high MPB activity in the state. Although MPB is leveling out in ponderosa pine, there has been an increase of activity in bristlecone pine.

Douglas-fir beetle continues to advance at mid-level elevations. We are seeing activity in the eastern San Juan Mountains and western Sangre De Cristo Mountain ranges.

The fir engraver beetle continues to advance in both the western Sangre De Cristo's and eastern San Juan's in white fir and subalpine fir. Unlike piñon and ponderosa timber stands, spruce/fir stands remain overstocked and unhealthy.

Spruce Beetle

Spruce beetle activity has advanced throughout the SLV and is of great concern due to the beetles' rate of spread. Roughly 2,000 acres in the Rio Grande National Forest in Conejos County have an estimated mortality of 100 percent. Salvage treatments are underway.

Thinning and preventive spraying continue to be the principal tool for prevention and control of bark beetles.

For more information, please visit the CSFS What is Wrong with My Tree? webpage.