Termite Treatment Practices In Low-Risk Areas

The common practice of pre-treating structures to prevent subterranean termites with less than label dosages may be a relic of the past in many low-risk areas of the United States, according to a study by Penn State entomologists.

There are two principle reasons for this. First, for many homes that are built in low-risk areas, it is unlikely that subterranean termites will surface until long after the toxicant has degraded. According to Penn State’s Dr. Robert Snetsinger, in low-risk areas such as subdivisions built on farmland, 30 or more years could elapse before conditions are conducive for termites.

Second, in high-risk areas (local termite “hot spots”), the integrity of a continuous toxic barrier with current termiticides is in question considering the variables in building practices, soil profile and distribution of termiticide even when applied according to label. The toxic barrier under a slab is only 1/8th of an inch deep when properly applied according to the label. It is anything but continuous by the time workmen have left the site. In Snetsinger’s opinion, pretreatment may be an unwarranted expenditure for homeowners in low-risk areas.

MISLEADING RISK MAPS. My Myth Conceptions article of April 1989 stated that Snetsinger and Carlos Roserio (now a professor of entomology at the University of Puerto Rico) reported on the misleading nature of the commonly published distributional risk maps of subterranean termites in the United States. They had surveyed homes in Center County, Pa., and found that the incidence of termites was far below the figures projected in the widely used risk maps. While this was for only one county, a forthcoming research report by Professor Hipollito-Farrill and Dr. Snetsinger will spell out the high-risk conditions more broadly.

In my opinion, the most important variable is the fate of the toxic molecule in soils. In my January 1992 Myth Con-ceptions column, I reported on a study by Dr. Charles Blake at the Massachusetts Institute of Technology in which he found that R. flavipes termites could not survive very long in soil with a pH above 8.7 or below 2.3. Adverse soil conditions exist in many parts of the country. The soil in a large housing development in Pennsylvania had been badly contaminated with heavy metals from a nearby smelter. For a century, belching smokestacks polluted the soil in much of the nation with acidic contam-inants. Incidentally, this, along with acid rain, may have affected the bird population by reducing calcium in the food chain that is needed for egg shell development. Of course, DDT got blamed.

When he was in quality control for a major food plant in Pennsylvania, Greg Baumann, now with NPCA, found that surface water in Harrisburg, Pa., had a pH of 4.6. In reports from 426 water authorities in the state, he learned that the pH of water in rivers and lakes ranged from 4 to 9.3 and that treated water varied from 4.4 to 10.6

According to Dr. Hanif Gulmahamad of Terminix, Arizona soils are fairly alkaline. They possess all the mechanisms for rapid degradation of termiticides: high temperature, high alkalinity and low organic content (to which toxicants usually bind).

Considering the susceptibility of all current termiticides to high pH levels, is it reasonable to expect serious control of termites many years after construction, especially in low-risk areas? At a National Conference on Urban Entomology in 1998, several papers described how the content of organic carbon and clay and the pH level in various types of soils can profoundly effect the longevity of current termiticides, especially at below-label rates. According to a news release by NPCA, builders who often contract with the lowest bidder for pretreating new homes for termite control, will be held responsible for failures.

THE “GAP-FREE” BARRIER. I believe that it is virtually impossible to positively protect buildings with “gap-free” toxic soil barriers. An erratic distribution of toxicant in the backfill hodgepoge is no barrier for hungry termites foraging in the neighborhood. It is a futile attempt (and a waste of many gallons of termiticide) to prevent termites in low-risk areas. Gulmahamad suggests that the PCO, for a modest figure, give a contract for annual inspection of the new building, placing monitoring devices at strategic locations and treating the infested areas only if and when termites appear.

On the other hand, Dr. Roger Gold of Texas A&M University, while agreeing that some agricultural soils in Arizona are low-risk areas, believes that termites in foothill locations will explore a newly poured slab. Until more is known about the complex conditions in soils which favor termites, he believes that the cost of pretreatment only at maximum label rates is still worthwhile. Even an extra year of protection after the toxicant has failed is worthwhile compared with the cost of damage.

Harry Katz, a contributing editor to PCT, may be contacted at Berkshire E-3076, Deerfield Beach FL 33442, 954/427-9716.