Myth Behavior

Zero to trace amount of termiticides were found in the majority of core samples taken by Mississippi regulators in 1989. Some of the tests, however, proved to have levels far in excess of legal limits.

There’s no question that operators should be penalized for such gross undertreatment or overtreatment, an obvious abuse of label and customer trust. Underdosing may be the biggest single reason for the increase in termite complaints. The failure to follow the label leaves gaps of untreated soil which termites easily breach.

There are cases, however, in which core tests show less than legal levels, based on parts per million (ppm), even after a proper treatment. All soils don’t weight the same. A cubic foot of a heavy soil is treated with the same volume (and weight of toxicant) as a cubic foot of lighter soil. The percentage of toxicant in the lighter weight soil is therefore higher than in the heavy soil. Theoretically and legally, the wrong ppm figure could damage a PCO’s case in court, even though this discrepancy may not be significant.

However, another matter dealing with the fate of termiticides in the soil is very significant. Test results indicate the residual life of early chlordane (code 1068) in soil exceeds 30 years. I believe there are two reasons for this extended control period.

One is the ability of chlordane emulsion to penetrate substantially beyond the point of injection. This was possible because the emulsion held its integrity long enough to creep into nearby sites. The key to the stability of the emulsion was the solvent system in chlordane, which was slow to volatilize. An emulsion breaks if the emulsifier of solvent breaks down and the toxicant then freezes in position. Neither even occurred with cholordane. It is a "myth conception" that the innocuous word "inert" in the ingredient statement is of little significance. It may be as important as the toxicant itself in maintaining the integrity of your guarantee when controlling termites.

A second factor. Another reason for the phenomenal success of early chlordane as a soil toxicant was the impurities in the mixture, including heptachlor, heptachlor epoxy, and other potent toxicants.

Refined chlordane, with alpha and gamma isomers and without heptachlor or other insecticidal isomers, was tested in Mississippi. Two test plots, at the 1 and .25 percent concentration, failed after 12 years.

Early tests of the "dirty" 1068 (chlordane) compound on animals were frightening. Mice were readily killed with dermal applications. At Penn State University, researcher Hubert Frings was blinded in one eye while conducting tests on mice. It is no wonder that the original test plots were still working more than 30 years later.

Fortunately, the manufacturer was later ale to purify its product. PCOs then used the ‘refined’ grade for indoor use only. The cheaper, dark version was used in agriculture and turf markets.

The results of tests done on mice with the original chlordane could not be replicated with the refined grades. Incidentally, the negative results of these tests with refined chlordane were published in time for Rachel Carson to include in her book Silent Spring. She elected to pass over these tests and described only the early tests in an eloquent fashion.

In my Myth Conception article in August, 1981, I ascribed the success of chlordane to its repellency. This was based on a publication by termite experts Ray Beal and Virgil Smith, in which they tested the early version of chlordane. Recent studies by researchers Nan-Yao Su and Susan Jones proved my "myth conception" to be a "myth conception." Refined chlordane is not as repellent as I had thought.

Furthermore, Su and other have found newer termiticides to be more acutely toxic as soil toxicants than present-day chlordane. Chlorpyrifos killed at 48 ppm and was not repellent; and permethrin is repellent at only 1 ppm in the soil.

So why so many failures? Apparently because the barrier in the soil was not continuous. Perhaps a component in the emulsion fails and the emulsion is broken. This arrests the movement which would have equilibrated beyond the point of injection and prevented gaps from developing in the barrier.

Perhaps the ability of some of the newer termiticides to be absorbed onto and bind into organic components in the soil is stripping the solution of its toxicants before the solution creeps on. This possibility needs to be researched. In any case, the need for closer application sites in the outside backfill may be the answer. Spacing 6 or 8 inches apart, rather than 18 or 24 inches would be more likely to close these gaps.

New soil applicators are available which are likely to improve the distribution quality of termiticides considerably. Pest control operators are urged to discard their old soil treating systems for the new ones.

Conclusion. There are many unsolved questions facing pest control operators, academicians and regulatory personnel in the termite control field. We’ve all been subservient to "myth conceptions" long enough, and should be willing to adapt to new realities.

___ Harry Katz

The author, a well-known pest control industry consultant, is a contributing editor to Pest Control Technology Magazine.