About the SFMGA

Sunday, June 01, 2003

Bark Beetle Info (From a handout supplied by Laurie McGrath)

What causes it?

Trees weakened by stress are more susceptible to disease and insect attacks than a healthy tree. Many conditions can cause stress, including drought, overcrowding, transplanting, soil compaction from construction, or even lightning damage.

Bark beetles (also known as Ips beetles or engraver beetles) attack primarily weakened, damaged, or dying PiƱon and Ponderosa pines. The beetles typically attack
the trunk or large branches, boring through the bark to create galleries where the female can lay eggs in the soft tissue beneath the bark. The beetles also introduce yeasts, bacteria, or fungi, such as Blue Stain Fungus, which can grow into and block the water flow in the tree’s tissue. The combination of tissue damage and fungus growth is fatal.

What can I do?

Inspect your trees

Look at tree vigor, color, new growth, and general condition. If the upper part of a tree looks faded or gray, if you see oozing red-colored sap or resin called pitch tubes or dust that looks like sawdust (boring dust) around the trunk or in the crevices of the bark, contact a licensed arborist or your County Extension agent.

Removing diseased trees protects your healthy trees and can potentially minimize populations.

Water

In our current drought conditions, our trees need supplemental water to prevent stress. Irrigate once a month during the winter and every 2-3 weeks during the summer.

Mulch

This reduces stress by providing a stable, cool root environment. Mulch retains soil moisture, prevents mechanical damage, and reduces competition form weeds or turf.

Mulch 2-4 inches deep with materials such as shredded leaves or wood chips, extending as far from the base of the tree as possible. Root systems often extend wider than the branches of a tree.

Fertilize

Feeding your trees will provide minor and major nutrients that can help ward off stress damage. Consult your nursery Professional or Extension Hotline (471-6251 in Santa Fe County) for the best information for your soil type and pH.

Spray

According to the US Forest Service, the insecticide Carbaryl (brand name Sevin) can prevent bark beetle infestation. Spraying with versions of Sevin available to home gardeners may not be as effective as commercial grades. Permethrin (brand name Astro) is also recommended, but has a shorter residual effectiveness than Carbaryl.

Application can be done by a licensed arborist or pest control applicator, and will have to be repeated annually.

What if my tree dies?


Remove it as soon as possible to keep populations down. Spraying the tree will NOT cure it or get rid of the larvae that will become another generation of beetles. Bury the infested wood or solarize (sterilize) it to kill the larvae.

To solarize/sterilize: pile the cut wood on black plastic. Piles should be no higher or wider than 4 feet. Cover the pile with CLEAR plastic and fold the edges of both layers of plastic together or cover with dirt to seal in the insects. Leave the wood covered for 45 days. This will allow time for the heat of the sun to kill the beetles and larvae. You can then use the wood for firewood without fear of spreading the insects.

Looking ahead:

In the space where the tree(s) once lived, you can plant seeds of native grasses or wildflowers. Or you can plant a replacement tree. Select a different species that is not susceptible to the bark beetle and adds diversity to your landscape. Recommended replacements include Austrian, Bristle Cone, Bosnian, or Mugo pines. Curl Leaf Mahogany or Red Berried Mahonia are two attractive shrubs that can be quite large at maturity.

Need more information? Call the Hotline at 471-6251.