Dennis R. Ring, Gregg Henderson and Charles R. McCown

The invasive Formosan subterranean termite eats the centers of living trees and builds carton nests inside them. Additionally, it is considered the most destructive insect in Louisiana, attacking the wood and paper in structures. Thus, infested trees may serve as reservoirs for termites to attack structures.

The state of Louisiana has taken steps to reduce the numbers of termites in trees on public lands. This program consists of drilling into trees in the Greater Lake Charles and Greater New Orleans areas and treating them with insecticide foam. LSU AgCenter personnel selected the trees, examined them after treatment and evaluated the results.

Trees to be evaluated were selected in 2000 using visual inspection for evidence of termites in at least three locations on the outside of the tree. The species of termite attacking a tree and tree species were determined. Selected trees were drilled and treated by licensed pest management professionals. AgCenter personnel treated other infested trees with water as experimental controls.

The selected trees were inspected after treatment every year for six years for evidence of termites to evaluate the effectiveness of the treatments. Formosan subterranean termite infestations were not found in 70 percent of the trees treated with Termidor 12 months after treatment and in 58 percent of the trees six years after Termidor treatment. Formosan subterranean termite infestations were not found in 65 percent of the trees treated with Premise 12 months after treatment; however, termite infestations were absent in less than 50 percent of these trees after three years. Formosan subterranean termite infestations were not found in 13 percent of water-treated control trees 12 months after treatment, and 13 percent to 20 percent of the water-treated trees remained without infestation for the duration of the study.

Because the tree treatment program was developed to control termites already in trees, it was considered a remedial program. The success of most integrated pest management programs, however, depends on preventative measures, when possible. Preventing termite invasion into trees is unfortunately a very difficult task. Termites can travel along the tree roots, which provide a natural pathway, or invade at points far from where any chemical treatment was applied. If the plants are young enough, we can employ a treatment in the soil where the plant ball will set. This treatment measure should be considered when dealing with new plantings in termite-infested areas.

Another preventative measure is to use plants less preferred by termites. Through this program we checked more than 1,800 trees for infestations by termites. These data show  Formosan subterranean termites showed a preference for pecan trees. Moreover, trees that produce nuts or fruits for human consumption cannot be chemically treated as described. The products used in this study are not labeled for use on nut and fruit trees. It would be wise to choose plants less preferred and to keep a vigilant eye for infestations as trees grow.

In addition to the success in reducing Formosan subterranean termite infestations in trees, considerable success has also been achieved in educating home owners in the Greater Lake Charles and Greater New Orleans areas. Another benefit of the program was the training and experience pest management professionals gained in treating trees for Formosan subterranean termites. This program may also serve as a basis for other programs to treat termites in trees.
 
Dennis R. Ring, Professor; Gregg Henderson, Paul K. Adams Professor; and Charles R. McCown, Extension Associate, Department of Entomology, LSU AgCenter, Baton Rouge, La.

(This article was published in the fall 2007 issue of Louisiana Agriculture.)