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Keeping trees healthy can help prevent bark beetle infestation

The damage done by pine bark beetles is generally not evident until long after the attacks have begun and the trees are dead. There have been reports on damage sightings in Citrus Hills, the Highlands, Sugarmill Woods, and Pine Ridge. To prevent additional damage, when you see this type of damage have the trees removed to prevent spreading of the beetles and further colonization into other pine trees.

What are pine bark beetles? They are slender, white, segmented grubs with brownish heads and rather prominent jaws. These larvae produce the chewing noises and piles of wood-colored sawdust that frequently cause alarm.

There are more than 600 beetles in the Scolytidae family commonly called bark beetles. To identify each species is difficult because nearly all bark beetles are black or brown, hard-shelled and vary from one-eighth to one-third of an inch long. The similarities in their life cycles and the damage they cause often make species determination unnecessary for making control decisions.

What do they do? Mature bark beetles bore through the bark to the cambium layer of trees in the right condition. Females form a tunnel between the bark and wood and lay their eggs. As the grubs hatch, they burrow away from the egg tunnel and feed on the live bark tissue and the outer layers of the wood. They call this network of egg and larval tunnels beneath the bark a gallery.

The numerous BB size holes in the bark of infested trees is a sign that many beetles have grown, made exit holes and flown off to new breeding sites. One to six generations per year is common, depending on species. In general, bark beetles infest trees that are weak or dying because of stress from such things as storms, drought, disease, smog, mechanical injury or root damage from nearby construction. They are also drawn to recently cut wood that still has bark.

Where the beetles first attack the bark, they produce curious looking pitch tubes. Some beetles become trapped in this sap and die. A healthy tree creates enough sap to prevent successful attack by many beetles, but sometimes, by overwhelming numbers alone, bark beetles are able to kill healthy trees. This can occur to trees that are near heavily infested breeding sites. Once a bark beetle is established in a tree, it emits a chemical called pheromone, which attracts other beetles to the tree. Once infested, trees rarely recover, and control efforts are usually futile. Bark beetles do not attack trees and wood that are dead and dried or recently cut wood if the bark is removed.

Other common types of bark beetles are listed below along with characteristics which should help you identify them.

Ips beetles, commonly called engraver beetles, are different from other bark beetles by their scooped-out hind ends. Ips galleries, found in pines, have egg tunnels the shape of an H or Y. Though capable of attacking the entire tree, Ips beetles are usually confined to the crown.

Southern pine beetle outbreaks can occur after long dry spells or poor forest management. This beetle's main attack area is the mid- and upper portion of the trunk. Every age and size pine could be a host. The egg and larval tunnel of this beetle has an unorganized pattern. Keeping trees healthy and vigorous will reduce outbreaks and tree losses.

The black turpentine beetle is rather large for a bark beetle, about a third of an inch long. It attacks pines at the base of the trunk and may also breed in stumps. Black turpentine beetle grubs feed together and carve large patches under the bark. A common sign of this attack is the presence of a globe of sap, about { inch in diameter, at the exit hole. Sometimes there will be large numbers of white pitch globs on the dark bark.

Other common bark beetles include: shothole borer, which attacks fruit trees, wild cherry, serviceberry, and occasionly elms; peach bark beetles are found in stone fruits, mountain ash, elm and mulberry; pityogenes spp. and pityophorus spp. in pines; phloeosinus spp. in cypress and junipers; ash bark beetles in ash; birch bark beetles in birch, beech, wild cherry and red gum; hickory bark beetles in hickory.

Also, there are many other species which may attack shade trees and wooded areas from time to time.

On healthy trees, bark beetles may attack individual twigs and branches that are dying from shading out or other causes. For example, some species breed only in dead or dying twigs, branches, and limbs of pines. These bark beetles will not breed in live branches, and thus are not a progressive destructive threat to healthy parts of trees.

Once a tree becomes infested with bark beetles, it usually dies rapidly. Bark beetles attack weakened, stressed, or dying trees. Preventive measures include: maintaining healthy, vigorous trees by trimming dead or weakened limbs; eliminating beetle breeding sites, such as recently dead or cut trees, limbs, slash and firewood with bark; and applying residual insecticides to susceptible but as yet uninfested trees, especially those under stress and therefore attractive to bark beetles. Treating infested materials before beetles emerge will kill them as they chew their exit holes.

Contact a professional for insecticidal recommendations or to find out about microinjection system control. To protect yourself when choosing a professional, look for someone that has been in tree care for a long time, has liability and workers' compensation insurance, is certified and licensed by the state and county. True professionals will be a member of the chamber of commerce and the Better Business Federation.

_ Editor's note: This is one of an occasional column on tree care written by Gil and Ray Stanage of A-1 United Tree Experts. Their background includes 30 years of training and experience in tree care. Other items will appear from time to time. Direct questions to them at by e-mail at: or call 726-7966.