The black turpentine beetles (Dendroctonus terebrans) is the largest pine beetle native to the U.S.. And while turpentine beetles are certainly tree pests, they are often considered secondary pests due to the fact that their ideal target is freshly cut pine stumps, stressed or weakened trees. Drought or fire stress, disease, previous pest infestation or storm damage all contribute to a tree’s susceptibility for colonization by black turpentine beetles. They are generally known to be less aggressive than their close relatives the southern pine beetle and will often be found colonizing a tree previously infested with southern pine beetles. Populations sometimes increase to levels where even healthy trees become infested.
The black turpentine beetle’s range extends as far north as Maine south to Florida and west to Missouri, Arkansas and eastern Texas. The distribution corresponds to the range of its preferred host species: pitch pine, P. rigida; loblolly pine, P. taeda; shortleaf pine, P. echinata ; and slash pine, P.elliottii. In the southeast the most severe infestations usually occur on slash pines, while in the northeast the worst occurrences are found on pitch pine, Japanese black pine and Scots pine.
Adult beetles are stocky in appearance and cylindrical, they grow 5 to 10mm in length. Black turpentine beetles habitually colonize the base of trees, and most attacks are confined to the lower 2-3 feet of the trunk. If a tree has incurred damage from flooding it is not uncommon to find turpentine beetles attacking the root collar. It is characteristic of the species for the female to initialize colonization usually beginning in bark crevices. When boring begins the tree will counterattack by producing and releasing profuse amounts of resin and a “pitch tube” will develop. The pitch tube of the black turpentine beetle is usually about 1 inch in diameter, a successful attack will produce a hole in the center. Failed attempts will trap adult beetles within the flowing pitch. A small attack may not mortality wound a tree but successful attacks over time, larval feeding on the phloem will restrict nutrient flow and kill the tree.
Little is known about natural predators and biological controls for black turpentine beetle infestations. In a forest setting an effective cultural control would be removing weak or damaged trees from the stand, due to the beetle’s preference for weakened stock. Replant only trees which are not preferred hosts for bark beetles to prevent reinfestation. In urban and landscape settings the best prevention is to keep trees healthy with appropriate fertilization, disease and pest management and good pruning through your landscape management plan developed by your arborist. Make sure your trees get proper watering appropriate for the season, avoid situations where soil can become compacted and roots can be damaged. Plant a variety of species and keep them spaced properly to avoid deter a monocultural infestation; densely planting the same species can create a pest superhighway and makes them very susceptible to being wiped out by one pest or disease. Mulch and ground covers can be useful to fill in bare areas, conserve soil and aid in moisture retention, use with care and under the guidance of your arborist.
If you have concerns regarding the health of trees on your property or questions about pests contact your arborist and visit http://www.savatree.com/insect-mite-treatments.html.