Laboratory and field studies with sorptive dusts for the control of arthropods affecting man and animal.

In laboratory studies carried out to determine the effectiveness of various inert dusts for the control of arthropods affecting man and animal, 110 dust compounds were evaluated. A synthetic silica aerogel, SG 67, used industrially as a flatting agent for lacquers and as an antiblocking agent for inks and paper coatings, was found singularly effective. The compound is a highly porous, finely divided, amorphous type of silica aerogel. It is odorless, white, has an average particle size of 3 micra, a surface area of 300 square meters per gram, and when packed has a density of 4.5 pounds per cubic foot. One pound of the compound will adsorb 2.55 pounds of oil. The compound is composed of 95.3% silica aerogel with 4.7% ammonium fluosilicate impregnated in less than a continuous monomolecular film on the internal surfaces. The ammonium fluosilicate, originally added for industrial purposes completely unrelated to arthropod control, gives the compound a strong positive charge that enables it to adhere exceptionally well to the bodies of arthropods, reptiles, birds and mammals and to the vertical and horizontal surfaces of almost all building and construction materials. Additionally, the ammonium fluosilicate greatly increases the insecticidal effectiveness of the dust compound, but does not detract from the ability of the silica aerogel particles to adsorb the lipids from the epicuticle. When arthropods crawl through the compound, the compound adsorbs the lipid layer and death due to resultant abnormal water losses ensues. Rapid death due to desiccation has been accomplished experimentally with German (Blattella germanica (L.)), American (Periplaneta americana (L.)), oriental (Blatta orientalis L.) and brown-banded (Supella supellectilium (Serv.)) cockroaches; cat (Ctenocephalides felis (Bouche)) and oriental rat (Xenopsylla cheopis (Rothsch.)) fleas; rodent (Haemolaelaps glasgowi (Ewing)) and cheese (Tyrophagus sp.) mites; brown dog (Rhipicephalus sanguineus (Latr.)) and spinose ear (Otobius megnini (Duges)) ticks; short-nosed cattle (Haematopinus eurysternus (Nitz.)) and cattle tail (H. quadripertusus Fahrenholz) lice; conenose (Triatoma protracta (Uhler)) bugs and field (Acheta assimilis F.) crickets. German and brown-banded cockroaches, cat and oriental rat fleas and cheese mites exposed to SG 67 and held at 25%, 50%, 75% and 100% humidities all died in the same period of time at each humidity, and at 100% humidity lost only slightly less weight than when held at 25%, 50% and 75% humidities. Male and female German, American, oriental and brown-banded cockroaches discontinuously exposed to SG 67 lost less weight than continuously exposed male and female German, American, oriental and brown-banded cockroaches. Samples of SG 67 held at 25%, 50%, 75% and 100% humidities, for a period of 4026 hours, adsorbed no moisture at 25%, 50% and 75% humidities, but adsorbed 168.13% moisture at 100% humidity. Adult male German cockroaches and adult male and female, unfed cat and oriental rat fleas exposed to equal amounts of the saturated test compound and held at 100% humidity for 24 hours were all dead within the 24 hours. The German cockroaches lost 31.03% of their body weight and the cat and oriental rat fleas lost 29.29% and 48.36% of their body weight, respectively. Untreated German cockroaches lost 2.55% of their body weight and the untreated cat and oriental rat fleas lost 10.48% and 6.87% of their body weight, respectively. Dead, dust-treated cat and oriental rat fleas and conenose bugs lost weight more rapidly than untreated dead specimens of the same species. German and brown-banded cockroaches continuously exposed to SG 67 at 10 different temperatures ranging from 5 °C to 50 °C with humidities ranging from 16% to 74% were knocked down and killed more rapidly at high temperatures and low humidities than at low temperatures and high humidities. The silica aerogel, SG 67, was found to be slightly less effective in knocking down and killing German and brown-banded cockroaches, cat and oriental rat fleas and cheese, rodent and snake mites after the compound had been used a number of times and left exposed to the atmosphere for a period of 900 days than when the compound had been kept for an equally long period of time unused and unexposed to the atmosphere. SG 67 has been successfully used for the control of pest arthropods infesting dwellings, hotels, motels, industrial plants, schools, hospitals, laboratories, zoos, ships, theaters, food markets and restaurants; for the control of ectoparasites infesting cats, dogs, birds, zoo animals, reptiles, horses, cattle and laboratory animals; and, pests infesting stored grains, preserved botanical specimens and mounted skins.