HOUSEBOAT HORROR

It’s no secret that subterranean termites can live above ground without soil contact. Provided there is food, a substrate for galleries and, most important, moisture, termites can survive and thrive indefinitely with no ground connection. Most companies have encountered this phenomenon before — sometimes with costly consequences. If the moisture condition due to rain seepage, plumbing leaks, etc., is not corrected, infestations can persist despite repeated efforts to treat the soil. Unfortunately, most laypersons believe that termites must regularly return to the soil in order to survive. Such misconceptions can hamper customer cooperation and bring into question the credibility of pest control companies.

PROVE IT. A few years ago, we discovered eastern subterranean termites infesting a house on a lake in Kentucky. Existence of a distinct, above-ground colony was obvious, considering that the 3,000-square-foot house was floating in 75 feet of water (see "A Watery Termite Tale," Pest Control, February 2000). When subterranean termites were discovered in yet another floating house, or, more correctly a houseboat — we figured it was worth a sequel.

THE BOAT. The unusual case involved a houseboat moored on Lake Cumberland, a large reservoir in south central Kentucky. The owner suspected he had termites but thought they only lived in soil. We inspected the 40-foot by 12-foot vessel last summer and sure enough, we found shelter tubes emerging from a wall inside the cabin. More intriguing was what we found below, in the cargo hold.

The hold was just wide enough to inspect by creeping along the wood sheathing, overlaying the metal hull. The wooden understructure had high moisture meter readings and several joists had fungal rhizomes covering the surface. Lying quietly on our backs, we could hear distinct "chewing" sounds, similar to those produced by mature old house borer larvae. Further inspection of the wood confirmed the presence of eastern subterranean termites, Reticulitermes flavipes. The remarkably clear sounds produced by the termites were apparently being amplified by the boat’s metal hull beneath the water. Termite shelter tubes, some more than an inch thick, were attached to metal framing along the sides of the boat. Closer examination revealed that some tubes were constructed mainly of rust particles from the aging metal.

THE TREATMENT. Various treatment options were discussed with the owner. Structural fumigations for wood-destroying insects are seldom done in Kentucky and the cost would have been prohibitive. Because of the limited access and cramped working conditions, we decided to bait the termites using Dow AgroSciences’ Sentricon® Termite Colony Elimination System.

On June 21, we installed two above-ground bait stations (Recruit™ AG) onto wooden members over active shelter tubes. Care was taken to minimize termite disturbance and entice them to begin feeding on the bait. Baits were lightly moistened with water and positioned so that the leading edge of the rolled paper matrix was in direct contact with the broken foraging tubes. Solvent-free (latex) caulk was used to seal around the outer base of the stations, since air infiltration can deter termites. We were unable to mount the rigid plastic stations over termite tubes on the narrow metal framing. Consequently, an experimental non-labeled installation was attempted using duct tape to affix shotgun shell lengths of bait directly to active shelter tubes.

When the baits were checked the following month (July 17, 2000), only one station had minor feeding. Live termites (and their chewing sounds) were still apparent. A third station was installed where termites were found between two abutting joists, all baits were re-moistened and we repeated our three-hour drive back to Lexington.

On Aug. 18, our efforts paid off. Although the original installations continued to be ignored, the station added July 17 sustained major feeding with about 11/3 bait tubes consumed. Hundreds of dead and dying termites were found within the station. Although termites seldom die in below-ground Sentricon stations, dead termites are sometimes recovered from above-ground stations, especially when there is no ground connection. A subsequent Sept. 3 inspection revealed additional feeding and live termites in another station, which was initially installed June 21. A smaller number of dead termites were also found in this station on Sept. 25. On this inspection, no live termites were detected and chewing sounds had ceased.

COLONY ELIMINATION? No attempt was made to estimate the size and relatedness of the termite population. Since there clearly was no ground connection, we were probably dealing with a rather small colony, perhaps less than 10,000 termites. Considering that they consumed about 60 grams of bait, more than enough hexaflumuron should have been delivered to destroy a small aerial colony. While the visual and audible absence of termites is encouraging, the only way to be certain is through subsequent inspection.

LESSONS LEARNED. The intent of this article was to definitively show, once again, that termites can persist above ground on alternative sources of moisture. The aerial colony probably originated from termite swarmers landing or crawling onto the boat’s decking. High wood moisture readings below decks indicated that the hold was poorly ventilated, with no place for the warm, moist air to go. Condensation would have been enhanced by the cold metal hull. Supplemental moisture may also have existed through some unknown leak.

Of course, conventional buildings afford many of their own opportunities for aerial termite habitation. Rain seepage, drainage problems, plumbing leaks, wood-to-earth contacts, external insulated finish systems (EIFS), condensation and poor ventilation can supply all the moisture needed for satellite clusters of termites to survive above ground and form new reproductives.

Elevated moisture levels are not always apparent, especially in modern construction. Tight, well-insulated and finished buildings can be nightmares to inspect and design flaws can reduce the drying potential of the building enclosure. In these cases, baits or non-repellent liquid termiticides are less likely to isolate termites above ground before the moisture condition is corrected. Hopefully, this article can be used to enlighten customers about the importance of moisture and enlist their cooperation.