Debugging New Orleans' Phone Lines

The Formosan termite, Coptotermes formosanus, has proven to be a formidable adversary for structural pest control professionals. Foraging aggressively and quickly reducing wooden structures to paper-thin sheaths, this species of termite is particularly problematic in the area in and around New Orleans, La.

The port of New Orleans has been identified as one of several probable points of introduction to the United States for this termite, which is native to Asia (La Fage 1987). The subtropical climate and predominantly wooden construction combine with the absence of natural population restraints to make New Orleans an ideal habitat for Formosan termites. Under these conditions, the number of Formosans has continued to rise. Annual surveys of swarming alates from 1989 to 1994 have documented a 950% increase in the number of swarming termites (Henderson 1994).

The continuing population increase and success of the Formosan termite may have contributed to the incidence of an unexpected problem. Formosans have been found in and around buried polyvinyl chloride (PVC) telecommunications conduits. The termites occasionally create holes in the PVC conduits and in the rubber seals around closure cases where conduits meet, causing water to leak into the system and leading to the possibility of short circuits and interruptions of service.

It is not clear why the termites are in these areas in the first place, although they have been observed using these routes as pathways into buildings. The threat of infestation to underground phone lines has been reported only in New Orleans and Hawaii, but is likely to be occurring in other areas afflicted with Formosan termites. Approximately 1% of the manholes (the access for maintenance workers to the conduits) in New Orleans have required repairs to Formosan-damaged equipment. The 1% figure does not represent the total manholes harboring termite infestations, only those requiring repair. The number of termite-infested manholes is likely to be higher as the manholes are inspected only after a problem has been identified. The average cost of repairing a termite-damaged conduit approaches $4,000, and repairs must often be repeated as the termites swarm.

SENDING OUT AN S.O.S. After treatments with traditional termiticides were found to be unsatisfactory, Bell South Telecommunications network, which serves New Orleans and vicinity, approached the LSU Agricultural Center and inquired about experimental termite baits being tested. The LSU Agricultural Center was quick to offer a helping hand in this matter, and widened its termite bait experiments to include underground cables.

The baits tested were either 100 parts per million (ppm) or 10 ppm sulfluramid on a cardboard matrix, and were provided by FMC Corporation. The 10-ppm rolls were substituted for 100-ppm rolls midway through this project. Baits were placed only in manholes with Formosan termites present, and were positioned directly in the path of foragers. Baiting a manhole depended on our being notified of the infestation. Thus, the length of time each manhole was in the study varied from 100 days to 640 days. Subsequently, the baits were inspected on a monthly basis.

Baits were removed and replaced after termites had stopped feeding or adverse conditions such as fungi developed on the cardboard. Baits that had been attacked by termites were dried, cleaned of debris, and then weighed. Occasionally, actual weights were replaced with visual estimates of consumption made in the field, because some baits increased in weight after being partially consumed by termites due to mud and frass deposited in the bait.

The accompanying table summarizes the results from August 1993 through June 1995, showing complete absence of termites being achieved in as little as 100 days (site TR-018) and termite activity and bait feeding continuing as long as 640 days (sites TR-001 and TR-002). Suppression ratings were based on the change in the number of termites observed in our last three monthly inspections (April, May and June 1995). Suppression ratings were:

EXCELLENT RESULTS. All locations had reductions in termite activity after exposure to sulfluramid, and the general trend is towards control of the infestation. However, given that we did not compromise the phone company (or its clientele) by setting up controls, our results must be considered as tentative in nature.

The total consumption of sulfluramid-treated cardboard does not correlate well with the degree of suppression, which may be a reflection of the size of the colonies being baited. However, it cannot be dismissed that the termites may have simply moved away from the baits. Field data on Formosan termite-infested cypress trees indicate colony elimination can occur with as little as 8.5 grams of sulfluramid bait (100 ppm) ingestion (Henderson and Forschler, in preparation).

The Formosan termite situation in the manholes lends itself to the use of a slow-acting toxicant like the metabolic inhibitor sulfluramid. Exposure to and ingestion of baits containing sulfluramid by termites is maximized in the manholes because food choices are limited.

Baits are preferable to conventional methods of controlling termites in manholes because they minimize the amount of toxicant used and confine it to a cardboard matrix, thus eliminating problems associated with perpetually wet and often submerged conditions such as the dilution or washing away of termiticides. Compared to conventional control methods, baits also reduce risks of contamination to local ground water. Baits are safer to work with in confined spaces, because there are no fumes. This reduces incidental exposure to the applicator and service technicians working in the manholes.

Sulfluramid shows great promise as an effective control agent against Formosan termites, especially when provided in a food matrix in areas lacking other food choices. PCT

REFERENCES

Henderson, G. 1994. The Formosan termite flight of 1995 in New Orleans: The biggest yet. Louisiana Pest Control Association News 125: 23.

La Fage, J.P. 1987. Practical considerations of the Formosan subterranean termite in Louisiana: a 30-year-old problem (pp. 37-42). In: Biology and Control of the Formosan Subterranean Termite (M. Tamashiro and N.Y. Su, eds). College of Tropical Agriculture and Human Resources. Research Extension Series 083.