Western Balsam Bark Beetle

The Western Balsam Bark Beetle (Dryocoetes confusus) is a notorious pest that inflicts damage on fir and spruce trees, posing ecological threats to forest ecosystems.

Host Plants

The primary host of the Western Balsam Bark Beetle is the subalpine fir (Abies lasiocarpa) as well as other true fir trees.  Western balsam bark beetles typically attack trees weakened by root disease, drought, wind breakage, and other damaging factors.

Regions impacted

This pest is found throughout the Western United States, including in the Rocky Mountain region and the Pacific Northwest. It can also be found in western Canada.

Description

The Western Balsam Bark Beetle is a small, shiny dark beetle. Adults measure about 1/6 inch (3.4 mm) in length. They have a slightly elongated and cylindrical body shape typical of bark beetles, with the head often concealed from view by the pronotum when viewed from above. The wing covers’ rear edges are rounded without spines, and both male and female beetles possess “hairy” patches on the front of their heads. The larvae are white, legless, and have a brown head.

Life Cycle

The Western Balsam Bark Beetle’s life cycle consists of four stages: egg, larva, pupa, and adult. This beetle typically completes one generation per year, but the life cycle can extend to two years in cooler climates or higher elevations.

• Egg: The process begins when adult females bore into the bark of host trees to create egg galleries. they construct egg galleries that radiate from the nuptial chamber (where they mated), forming a star-shaped gallery.
• Larva: Once the eggs hatch, the larvae feed on the inner bark of the tree, creating their own feeding galleries that extend outward from the egg gallery. This feeding can girdle and kill the tree if the infestation is severe enough. The larval stage can last for several weeks to a few months, depending on the temperature and food availability.
• Pupa: After the larvae have completed their development, they create pupal chambers at the end of their feeding galleries, where they transform into pupae. This is a resting stage as the larvae metamorphose into adults.
• Adult: Adult beetles emerge from their pupal chambers by boring straight through the bark to the outside of the tree. They then fly to seek new host trees and mate. This usually happens during warm and dry periods of the summer.

It’s important to note that environmental conditions, particularly temperature, can greatly influence the timing and duration of these life cycle stages.

Damage and Detection

Damage:

The Western Balsam Bark Beetle, like other bark beetles, can cause significant damage to its host trees.  If the infestation is severe enough, this feeding can girdle the tree, cutting off the flow of nutrients and water, and causing the tree to die.

Detection:

There are several signs that a tree might be infested with Western Balsam Bark Beetles.

• Small amounts of sap may stream for about an inch below the entrance hole.
• The presence of exit holes in the bark where adult beetles have emerged.
• Evidence of the beetle’s egg galleries beneath the bark. These are usually revealed if the bark falls off or is removed.
• Frass, or a combination of beetle excrement and sawdust, may be found at the base of the tree or in the bark’s crevices.

It’s important to remember that by the time these signs are visible, the damage is often severe, and it may be too late to save the tree. That’s why preventive measures are so crucial in managing these pests.

Prevention and Control

Controlling the Western Balsam Bark Beetle and preventing infestations can be challenging, but there are several strategies that can be effective:

• Maintain Tree Health: Healthy trees are less likely to be infested by bark beetles. Practices that promote tree health include proper watering, fertilizing, and pruning. Removing any diseased or damaged trees can also prevent beetles from establishing a population in your area.
• Sanitation and Removal: Removing infested trees and those that are likely to be infested can reduce beetle populations and prevent them from spreading to healthy trees. It’s crucial to properly dispose of these trees, as beetles can continue to breed in downed or dead trees. This may involve chipping, burning, burying the wood, or treating it with pesticides.
• Pheromone Traps: Bark beetles, including the Western Balsam Bark Beetle, use pheromones to communicate. These chemicals can be used in traps to monitor beetle populations and, in some cases, to divert beetles away from valuable trees.
• Chemical Control: Insecticides can be effective, but they should be used judiciously due to their potential effects on non-target organisms and the environment. They are generally most effective when applied before the beetles attack the trees. Always follow the label instructions when using any pesticide.
• Biological Control: Certain birds, insects, and other creatures are natural predators of bark beetles and can help control their populations. Efforts to protect and encourage these beneficial organisms can be an important part of an integrated pest management strategy.

Remember, effective management of Western Balsam Bark Beetle often involves a combination of these strategies. An integrated pest management (IPM) approach, which combines several different methods, is usually the most successful.