Managing and mitigating your beetle infestations to ensure healthy trees and reduce forest fire fuels
While beetles and other pests are a natural part of a balanced, healthy ecosystem, small changes in environmental factors can throw a balanced ecosystem out of whack while the ecosystem as a whole struggles to adjust. Historically consistent, cold temperatures kept the beetle (and other pest) populations in check by freezing and subsequently killing a high percentage of the larvae. However, with recent winter temperatures being higher than in the past, beetle populations increased. Coupled with forest fires that have left portions of the forest leaf burned and stressed, beetle populations have spiked in some areas.
Quite a few of the Douglas-fir (Pseudotsuga menziesii) forests of the western United States have turned brown from the Douglas-Fir Beetle (DFB) (Dendroctonus pseudotsugae). The DFB is a common bark beetle that kills Douglas-fir trees. The cylindrical-shaped beetle is about ¼ inch long with a black body and reddish brown wings. The beetles winter either as larvae or in adult form and emerge during the spring when temperatures rise to around 60*F. Most beetles have one life cycle but with longer, warmer seasons starting earlier the DFB is achieving two life cycles per season more frequently which is drastically contributing to their devastation.
The Beetle and the Damage Done
The DFB larvae feeds under the bark and can introduce fungi, yeasts and other organisms that that ultimately lead to the trees death. Visible reddish-orange frass can be seen in the furrows of the bark as an indicator, but this frass can be easily washed away and should not be used as a sole indicator for infestation. Pitch tubes are not always present but many trees will have pitch streaming down from the top of beetle infested areas on the tree. Needle color is also an indicator of infestation as the needles will transition from their normal healthy green to yellow into reddish-brown.
While the beetles traditionally attack damaged or weak trees when in normal populations, when large populations of DFB are present they will attack and kill in massive outbreaks that can kill thousands of trees. Large populations should be expected post wildfire.
Prevention and Management
To protect the value of your property and to help safeguard from unsafe levels of fuel build up from dead trees it becomes extremely important to address the issue head on and trust field experts to identify target trees and areas to prevent the spread of the beetle and promote a safe healthy stand.
The overall best management practice is to promote a vigorous stand by thinning. Prompt removal of damaged trees that will attract and be easy targets for the DFB is highly recommended. This includes windthrown, fire-damaged, diseased, or root-damaged, or defoliated Douglas-fir’s. When deemed necessary, trees can be protected by using the anti-aggregate pheromone methylcyclohexanone (MCH).
To ensure your trees health, consult the forestry experts at Firewise and TLC where we have been managing forests in the Mountain West region for over a decade. Whether thinning or applying MCH is deemed necessary we have the experience and the expertise to make sure that the correct management practice is applied.