Pinus: Pine Bark Beetles

Problem
Needles in the crown of the tree turn yellow at first, then turn brownish orange to reddish brown. Small holes appear in the trunk. Tubelike masses of pitch may also be present. When the bark near the holes or pitch tubes is cut away, legless grubs with brown heads may be found in tunnels under the bark.

Analysis
(Dendroctonus species)

Pine bark beetles feed primarily on pine, and occasionally on spruce and larch. Injured, weak, and dying trees are most susceptible to attack. Some species of bark beetles, known as turpentine beetles, create tubes of pitch on the lower bark of trees. Another species, the pine bark beetle, attacks the middle and upper trunk and does not create pitch tubes. Adult beetles of all species burrow under the bark, where they lay eggs. The larvae that hatch feed by tunnelling through the bark. They form pupae in their tunnels and emerge as adults. A few beetles in a tree will not kill it; however, many pitch tubes indicate that enough beetles are present to kill or seriously weaken it.

Solution
Severely infested trees should be removed and destroyed as soon as possible. If pitch tubes are present, smash them with a heavy rubber mallet to close the tunnel and squash the insects in the gallery beneath. Spray the trunk with an insecticide containing lindane. Keep the tree in good health by watering it thoroughly every 4 to 6 weeks during dry months. Fertilize weakened trees. Avoid injuring tree roots and trunk. Do not pile freshly cut pine wood or trimmings near trees because these attract beetles to the tree.