Healthy, well watered pines resist bark beetles such as western pine beetle and engraver beetles best, so protection in California centers on deep watering during drought, a mulch ring over the roots, avoiding root and trunk injuries, and removing infested trees promptly. Preventive insecticide sprays, applied by a licensed professional before beetles attack, are reserved for high value trees.

Why do bark beetles attack stressed pines?

Because drought, compacted soil, and root damage weaken a pine's main defense, the resin it uses to push boring insects back out. Long dry spells leave many California pines short of water and less able to fight off an attack.

How is a pine watered to resist beetles?

Deeply during dry spells, across the whole root zone. Soil is moistened 12 to 24 inches down and out beyond the dripline, and mulch 2 to 3 inches deep, kept off the trunk, holds that moisture. Where summer watering is limited, Hydretain Root Zone Moisture Manager, sprayed over the root zone from a hose end sprayer and watered in heavily, stretches the time between waterings for up to 3 months.

What are the signs of a bark beetle attack?

Resin and dust on the trunk, then fading needles. Common signs include:

• Pitch tubes, small masses of resin where beetles bored in
• Reddish boring dust in bark crevices or at the base
• Sap oozing from small holes in the bark
• Needles fading from green to yellow, red, and then brown

Frequently Asked Questions

Can sprays save a pine that is already infested?

Rarely. Preventive sprays protect trees that have not yet been attacked, so an infested pine is usually removed.

Is firewood a risk to healthy pines?

Yes. Freshly cut pine with bark can carry beetles, so it is kept away from living pines.

When should pines be pruned to avoid drawing beetles?

In late fall or winter, so fresh wounds are not open while beetles are active.

Will fertilizing a pine keep beetles away?

Not on its own. Water matters more, since drought stress is what opens the door to beetles.