Bark beetle infestation can occur in forested locations generally east of the Cascade mountain range to forested areas east of the Rocky Mountains in Canada and the United States.
Certain aggressive bark beetles are capable of killing healthy trees. They do this by girdling the inner bark, introducing a lethal fungus into the tree, or both. One clear sign of a possible bark beetle problem is conifers with their foliage changing from green to yellow, brown or red. If bark beetles are found in such trees, either on your property or in the nearby forest, you may wish to consider implementing an integrated pest management (IPM) program. If you own a small property, e.g. a lot in a rural subdivision, you may wish to band together with other property owners and seek expert advice in implementing an area-wide IPM program that is large enough to be effective.


1: Diagnosis

Trees can die from many causes including attack by bark beetles. Some bark beetles naturally attack dying and distressed trees, so their presence may not indicate the true cause of death. Therefore, you must determine the cause of death in order to take the proper corrective action.

Bark beetles killing conifers on your property may include the mountain pine beetle (on any species of pine), the western pine beetle (mainly on ponderosa pine), the Douglas-fir beetle, and engraver beetles (usually on any species of pine).

Early identification of successful attack is critical. However, attacks on some trees may not be successful, and the trees may not be dying. Alternatively, a tree may be successfully attacked, but its foliage may remain green for a long time, even though it is effectively dead. Therefore, it is strongly recommended that you retain someone skilled in diagnosing bark beetle attack. This will include most forest health consultants, and those certified arborists and professional foresters that deal with pest problems.

Step 2: Disposal of Infested Trees

To interrupt the progress of an infestation, all infested trees on your property or in your community (and preferably also trees in nearby forests) must be removed and disposed of. Disposal can include harvesting, or falling infested trees and burning, or chipping them. If the bark will come off and alternative is to remove the bark and burn or chip it. Stumps should be cut as close to the ground as possible. This must be done by April - early May for most bark beetle species before they emerge to attack healthy trees. Check with your consultant for the correct timing in your area.

Some attacked trees may escape detection, and immigrant beetles may invade from the surrounding countryside. Your IPM program will probably not be successful unless you take further measures to protect the remaining trees.

Step 3: Stand Spacing - “Beetle Proofing”

For large properties over 1 – 3 hectares, spacing or “beetle proofing” is another option to help mitigate attack. The mountain pine beetle prefers to land and initiate attack under lower temperatures and light intensities, typical of dense stands. However, they tend to keep seeking hosts at higher levels of light and temperature. Spacing opens the stand allowing more solar energy into the stand raising both temperature and light intensity. It also increases tree vigor and vigorous trees are more successful at pitching out the beetles. The longer beetles fly, the higher their losses to predation and desiccation, and the lower their energy reserves when they finally do locate a host. The Canadian Forest Service recommends that dense stands be thinned to a uniform spacing of 4 or 5 metres between trees.

Step 4: Protecting the Remaining Trees with Insecticide

When used according to label instructions, the insecticide carbaryl (Sevin) is very effective in preventing attack by bark beetles. The spray may be applied at from April to early June depending on your location and bark beetle species, before the beetles fly, and should cover the entire trunk, well into the crown. The insecticide impregnates into the bark and can remain effective for up to a year. You may wish to spray only the most valuable trees, such as those that provide shade or visual pleasure. You may also protect your trees with repellent pheromones if you do not wish to use pesticides.

Step 5: Protecting the Remaining Trees with Repellent Pheromones

To prevent crowding, some bark beetles use a pheromone to post a No Vacancy sign to indicate to other bark beetles that the tree is full. When devices that release the pheromone are placed on non-infested healthy trees, other beetles “read” the false No Vacancy sign and move on.

Pherotech's Mountain Pine Beetle Repellant, also called the No Vacancy Pack - MPB, can be used to protect pines from attack by the mountain pine beetle. Extra protection can be obtained by applying the product to insecticide-treated trees.
 
Application of repellent pheromones must be completed before the beetles emerge to attack non-infested trees. At low elevations, the mountain pine beetle emerges in May through September with the peak flight in July. Therefore, depending on your location, we recommend that the verbenone pouch be attached in May and again in July to protect against mountain pine beetle attack. Check with your consultant for the correct timing in your area.

The verbenone pouch should be placed on the north or shady side of the tree as high as the applicator can reach. For high value trees two packs may be used and should be placed as high as the applicator can reach on the shady side of the tree.

Step 6: Post-Flight Diagnosis

Repeat step 1 at the end of October after beetle flight has ceased. If infested trees are found, the program should be run again next year. This may occur for several years. Eventually all of the trees outside the treatment area will probably be killed and the infestation will subside. The trees on your property may then be free to live another 100 years, or more.

Pherotech Inc.

Pherotech Inc is a British Columbia based developer, manufacturer and supplier of insect pheromone based pest management products including bark beetle pheromones and traps.

Bark Beetle Integrated Pest Management Timeline and Activity Table


1Timing depends on bark beetle species and location – effective for all bark beetle species
2For mountain pine beetle only – timing depends on location
2*May application optional
2**Suggested application timing for verbenone.