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Marin IJ Articles

Beware of pine bark needles

  • Karen Gideon
  • Many of Marin's neighborhoods were built in the '50s and '60s, and developers planted Monterey pine trees for fast growing landscapes and windbreaks. As these pines become stressed from aging, drought and climate warming they are more susceptible to disease and pests. Two pine bark beetles, the red turpentine beetle and the five spined ips, are common culprits in Marin County urban interface areas.

    The best way to check for pine bark beetles is to inspect your pine trees.


    The red volcano-like pitch tubes of the red turpentine beetles, Dendroctonus valens, are fairly easy to locate. Small numbers are rarely fatal to the tree. To find the adult beetles which are about ¼" long, dark red, and about the size of a grain of rice, you'll need to peel back the bark of an infected tree. There you will see "beetle galleries" — winding patterns of tunnels chewed by the beetle's strong mandibles and packed with sawdust. They create wide cave-like egg-laying tubes inside the bark near the tree base. This is a clear sign of infestation that disrupts the flow of nutrients in the inner bark, and can sign stress from insufficient cultural care or injuries to the tree.

    The California five spined ips (Ips confusus), part of the group of engraver beetles, also leaves an orange-brown boring dust in bark crevices. Look for fading foliage in the top half of your pine and evidence of fine sawdust about halfway up the trunk or on branches. This beetle attacks in the stem tips and canopy, high above ground, and is often overlooked by homeowners until the tree's crown begins to yellow, flag and die. They can be hard to spot. Their tunneled galleries are Y-shaped and the adults overwinter, using the pine trees as breeding material in the spring, producing multiple broods. The ips is capable of rapid, widespread reproduction and can kill the pine tree and spread to other pine trees.

    Because the deadly ips beetle lives under the protection of thick bark, little can be done once the tree is infested. You can prune limbs if the infestation is just starting, but once it is in the trunk, the tree needs to be removed. This must be done carefully to protect nearby pine trees that may also be stressed and susceptible. If the tree is chipped or cut for firewood, the remains need to be wrapped in thick, clear plastic sheeting and solarized for several months to kill resident beetles or larvae.

    Prevention is the best way to keep your pines healthy and beetle free.

    Protection from bark beetles requires good cultural practices to lessen susceptibility. Diversify your landscape and choose trees that are well suited to your environment. Research the care requirements — know the proper watering frequency and pruning needs. Improper planting or transplanting technique, poor site choice, or planting at the wrong time of the year all increase susceptibility to infestation.

    If you've had a beetle infestation in your yard, consider planting non-host trees. If you have a stand of pine trees, thin them so that the branches have plenty of light and circulating air. Avoid damage to your pine tree from sunburn, improper pruning, or physical injury. Irrigate your tree at the edge of your canopy, not by the trunk.

    Much is gained by the simple act of observation. Take a few minutes to check out the bark and canopy of your pines. And if you start to see changes, look for the signs of these two bark beetles. If your trees are large and well established, and you see a few indications of beetle activity, make note of it and continue to observe your trees. If your trees are small to medium in girth and you see multiple instances where the beetles have breached the bark, contact your local arborist.