Myth Conceptions

Dr. Ross described tests performed at Virginia Tech with standard formulations currently on the market and compared them with formulations without the active ingredient. Vapors of "blanks" of cyfluthrin (Tempo, without the active ingredient) flowable concentrate, cyfluthrin wettable powder and a permethrin aerosol were equal to or more repellent than the complete formulations. In the studies, the vapors of a permethrin aerosol and cyfluthrin flowable concentrate were more repellent than formulations of cyfluthrin wettable powders and emulsifiable concentrates. Test results showed that the vapors from the "blanks" of certain commonly used insecticides were more repellent to German cockroaches than vapors of the complete formulations.

An experiment with Baygon showed that the vapors from the inert ingredients alone were as effective in dispersing cockroaches as the marketed formulation. It is interesting to note that the same material (propoxur) in bait form is eagerly eaten by cockroaches and that it isn’t repellent in aerosol form where the inerts are the propellants.

What concerned Dr. Ross was the marked difference in behavior of resistant versus susceptible strains of cockroaches to inert ingredients. She suspects that this general loss of sensory perception is directly related to a resistance mechanism, although the possibility that behavioral changes developed independently of insecticide resistance cannot be ruled out. She believes that bioassays for behavior patterns of various resistant strains should be developed, in addition to continued studies on insecticide resistance.

OTHER EVIDENCE. I have long believed that our industry has entertained a "myth conception" about the importance of rating the value of topical tests of toxicants in acetone. In a test I performed with a specially prepared formulation of diazinon-less emulsifiable concentrate, I sprayed the diluted material on a large bush that was heavily infested with wasps. The result was that the bush remained wasp-free for the entire summer.

In another instance, when the EPA decided that 100 percent sodium fluoride was no longer acceptable in a roach and ant killer, I felt 40 percent sodium fluoride was strong enough and sent the EPA an application to register a product I packaged. In the application requested I registered the product as having 60 percent celite, a diatomaceous earth that is often used as a filler. Much to my delight the EPA registered the formulation.

Entomologist Don Reierson, of the University of California at Riverside, believes that inerts in a formulation can be more important than the active ingredient itself. The repellent effect of some inerts is more significant than the toxic value in many cases. In addition to tests with the active ingredient in acetone, EPA protocols for registration also include toxicity tests in which the insects are forced to rest on panels treated with the formulated product. Reierson believes that in the field many of the insects simply avoid the treated surfaces because of the presence of the inerts.

TIMES HAVE CHANGED. For decades pesticide formulations were made with solvents and emulsifiers developed for agricultural use. Formulators were more concerned at the time with the stability of the emulsion and other properties than with odor or repellency. The data from the early insecticides used in agriculture was the basis for registration of most of the pest control industry’s products.

Today the climate has changed totally. New products including emulsifiers, buffering agents, attractants, defoamers, adhesives, solubilizers, solvents, diluents, surfactants, etc., are critically assessed for odors, stains, stability, ability to penetrate the substrate, resistance to light, pH, irritation of skin, allergies and other reactions. Little information is available about the nature of the new breed of inerts, and after spending millions of dollars to develop formulations it is easy to see why companies are reluctant to do so. At least we can take solace in the fact that the ever-cautious EPA has assured us that these inerts pose no health hazard.

A MATTER OF SEMANTICS. A desiccant can be an inert filler in one formulation (as in my old roach and ant powder) and an active ingredient in another. Diatect, the new product with fresh water diatomaceous earth, for example, is considered 100 percent active ingredient. I described it previously as a low stress, non-repellent desiccant. In another Diatect product, a second active ingredient (pyrethrins) is added, thus making it a high-stress product.

In a similar case, entomologist Bill Robinson of Virginia Tech tested various emulsifiers with diazinon and found some increased the toxicity of the active ingredient, while others decreased the toxicity of the material.

A most outstanding example of the profound value of an inert ingredient is the new product Bora Care. The product contains an active ingredient (boron) which would penetrate only superficially in ordinary wood members if applied in a water base. However, when dissolved in a glycol base which evaporates very slowly, it continues to creep slowly below the surface. This active ingredient (boron) is effective against all wood-destroying organisms only because of the inert ingredient present. We should now see that our industry perception of the term "inert ingredient" on the label is indeed a "myth conception."

Harry Katz is a contributing editor to PCT magazine. If you would like Katz to speak at an upcoming conference or educational event, write: Harry Katz, Berkshire E #3076, Deerfield Beach, Fla. 33441, 305/427-9716.