Here are a few basic reminders. There are five species of pine bark beetles which seem to cause most of the havoc: the Southern pine beetle (Dendroctonus frontalis), ips engraver beetles (Ips avulsus, Ips calligraphus, and Ips grandicollis), and the black turpentine beetle (Dentroctonus terebrans). All spend most of their life cycles unseen, under the bark of the tree. The life cycles are simple: 1) adults chew throught the tree bark to lay eggs in sometimes very decorative and extensive galleries under the bark 2) after the eggs hatch, the larvae remain unseen, tunneling, eating, and girdling through the cambium 3) The pupae continue until the adult stage, at whitch time they chew their way out from under the bark to attack another tree. Within these few life-cycle steps, are the reasons for the tree’s death: 1) The girdling of the cambium causes damage to the water and nutrient pipelines of the tree 2) Larval feeding 3) Blue stain fungus brought into the tree by the attacking adults.
It is important to remember that despite the fact that all bark beetles can attack either healthy or dead/suffering trees, most appear to prefer trees which are dead or stressed. Most of the beetle activity occurs between March and September, or occasionally on very warm days in winter. Large attacks happen periodically about every five to twelve years. Outbreaks may occur following droughts, ice storms, or hurricanes, all of which are very stressful to the tree.
So, how can we, the homeowners, tell as early as possible, that our pine trees have suffered an attack from the pine bark beetles? As we walk through our garden admiring the beauty around us, we should monitor all our plants for various insect pests and diseases, as well. Those of us who have pines (especially Loblolly, Short leaf pine and Virginia pine) in our yard, will need to pay special attention to the ground around the trunk, as well as far up the trunk as possible. Also, stand at a little distance to view the crown of the tree to see the color of the needles.
On the ground and in the crevices of some of the bark, you may notice either white or reddish-brown sawdust. This is the result of the adult beetles chewing their way from the outside to construct egg galleries under the bark. As you inspect the trunk at eye level and higher, white pitch tubes may be evident (sometimes very small and hard to notice) in the cracks between the bark. As your eye moves into the crown, notice the color. The healthy pine tree has dark green needles. In the summer, if the tree is under attack, the pine needle color begins to change about three to four weeks after the attack has begun and it may take about three months for the crown to turn light green, yellow, and finally reddish brown, or completely dead and the pine needles begin to fall in great numbers. At times, the beetle attack may occur in late fall, and the tree can remain green throughout the winter, before showing the color change the following spring. In either case, the change of the needles to brown coincides with the exit of the adult pine bark beetle from the tree to attack another host. At this point, the tree is dead and should be taken down and removed.
There are several preventive steps that can be taken, most important of which is to keep the tree as healthy as possible:
* avoid soil compaction in the root zone
* avoid physical and mechanical injuries to the tree
* minimize competition for nutrients from vegetation in the root zone
* provide proper fertilization and mulching.
Good luck with the beautiful pine trees on your property. Keep your eyes open and stay ahead of these beetles.
Information about Extension Solutions for Homes and Gardens can be found on the University of Georgia Cooperative Extension website at www.caes.uga.edu/extension/cherokee or by contacting the Cherokee County Extension Office at 100 North St., Suite G21 in Canton at (770) 479-0418. The Georgia Extension Master Gardener Program is a volunteer training program offered through county offices of the University of Georgia Cooperative Extension.