Residual Action of Organic Insecticides

Fleck, Elmer E.

doi:10.1021/ie50460a029

Cited by 9 publications

(3 citation statements)

References 15 publications

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“…Decomposition, once started, continued even after the benzene had evaporated. Fleck (1948) confirmed these findings, and showed that the rate of decomposition of DDT in solution under the influence of ultra-violet light depended on the type of solvent. He also showed (Fleck, 1949) that decomposition by ultra-violet light gave a different product depending on whether air was present or absent, and that dehydrochlorination was not necessarily the first step involved.…”

Section: Department Ofsupporting

confidence: 66%

The Persistence and Fate of DDT on Foliage. I.—The Influence of Plant Wax on the Toxicity and Persistence of Deposits of DDT Crystals

Burt

Ward

1955

Bull. Entomol. Res.

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The persistence and toxicity of DDT crystals on thin layers of plant wax were studied. Deposits of crystalline DDT at rates of 2 to 8 microgm. per sq. cm. were applied to glass plates, plain or coated with a 0·5 μ layer of wax obtained from leaves of sisal or cabbage. The plates were stored for various periods at 18°C. and at 43°C. (representing temperature and tropical leaf-temperatures). DDT remaining after storage was estimated biologically by means of its contact action on adult Tribolium castaneum (Hbst.), and chemically by a modification of the Schechter-Haller method. At 18°C, there was no significant change in any of the deposits when estimated chemically. But biological estimation showed that, although the toxicity of the deposits on waxed plates was unchanged, that on glass plates was doubled after storage for eight days. The reason for this change was not discovered. At 43°C., the amount of DDT, estimated both chemically and biologically, diminished rapidly and was negligible after 26 days. The loss of toxicity at 43°C. was shown to be accompanied by loss of weight of the deposits. Loss at 43°C. from plain glass plates could be much reduced by storing them in an atmosphere saturated with DDT vapour. It appeared, therefore, that loss of toxicity at the higher temperature was due to volatilisation of DDT and not to decomposition.

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Section: Department Ofsupporting

confidence: 66%

The Persistence and Fate of DDT on Foliage. I.—The Influence of Plant Wax on the Toxicity and Persistence of Deposits of DDT Crystals

Burt

Ward

1955

Bull. Entomol. Res.

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“…The insecticide that enters the plant parts is not easily recognizable after it is released by the plant. Thus, to determine the residual action of an insecticide there is need to study its vapor pressure, sticking power, solubility, and absorption into the surface on which it is applied, as well as resistance to chemical change (4).…”

Section: Residual Action Op Pesticidesmentioning

confidence: 99%

Título en español.

Roldan¹

1959

JAUPR

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This paper reports the results obtained in studies carried out with spray deposits left by the insecticide Parathion on West Indian cherries. Although data are not final, it seems that Parathion applied at the rate of 1.5 pounds per 100 gallons of water per acre to West Indian cherries leaves a residue which is below the limit established for fruits by the Food and Drug Administration of the U. S. Department of Health, Education, and Welfare. The results thus far obtained indicate that Parathion is rapidly degraded under the conditions of these experiments. It seems too early to make any final recommendations. More experiments have to be performed, especially during other seasons of the year, so that results can be compared and critically evaluated.

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“…(a). Although it is decomposed by air in the presence of light or alkalis (Fleck, 1948), rotenone is not specially reactive and can be absorbed by bean leaves and carried to other parts of the plant, apparently unchanged (Fulton & Mason, 1937). D D T is rapidly decomposed by bases, but is otherwise stable.…”

Section: Physical Drug Actionmentioning

confidence: 99%

Particle Size of Insecticidal Suspensions and Their Contact Toxicity Iv. Mechanisms of Action of Different‐sized Particles

McIntosh

1951

Annals of Applied Biology

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Two earlier papers showed that in tests of suspensions by dipping, large crystals of D D T could kill grain beetles just as efficiently as colloidal DDT. But with rotenone, colloidal particles were far more toxic than large crystals; this difference was partly in their speeds of action. A third paper showed that in contact action the relative toxicity of small particles is increased by cooling the beetles after treatment. In tests by injection into milkweed bugs, particle size seemed to have no effect on toxicity of rotenone and D D T suspensions if the bugs were kept warm after treatment. In cool bugs, colloid acted more quickly than crystals, but the kills from the two types finally became the same. T h e time for this to come about was less for D D T than for rotenone and less still for D F D T , an analogue of DDT.An explanation of these results is now given. In the action of contact poisons, attention is given to the waxy layer on the outside of the cuticle. Contact poisons must first of all dissolve in this wax layer, and it is suggested that the difference in action between rotenone and D D T is due to a difference in their solubilities in wax.Small particles will always have the advantages, over large, of greater surface area and greater ability to enter openings in the body. With Oryzaephilus surinamensis, a main route of entry by rotenone into the body is possibly through the spiracles, and this may be why colloidal rotenone is so much more toxic than rotenone crystals. T h e solubility of rotenone in wax is thought to be small and if this is so, it will be easy to saturate the wax and the higher solubility of very small particles of rotenone will be of importance. The behaviour of rotenone particles of different sizes is therefore understandable.Entry through the body openings is evidently unimportant for DDT, because large crystals kill as quickly as small ones. Penetration must be through the general cuticle. It is suggested that the solubility of D D T in wax is very high, compared with rotenone ; the wax will not be easily saturated by D D T and small particles will not have the advantage of higher solubility, which is only helpful if saturation is reached.It is shown theoretically that if solubility (in wax) does decide the relative behaviour of different-sized poison particles, then colloidal poison should be more toxic, relative to crystalline poison, if the insects are kept cool after treatment than if they are kept warm.The following explanation is offered for the injection results. The blood of milkweed bugs contains free droplets of oil, and these are mainly responsible for carrying poison from injected crystals to the site of action. Colloidal poison probably diffuses there directly, and more quickly, in the aqueous phase of the blood. The difference in speeds of action of colloidal and crystalline poison will depend on the ratio of dose to solubility in oil. If this is large, saturation of the blood is easy, and * Present address. The author was seconded to New Haven during 1950.

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Residual Action of Organic Insecticides

Abstract: The residual action of nonvolatile organic insecticides is governed largely by their resistance to chemical change under field conditions.Oxidation has been shown to be a common cause of failure in pyrethrum, rotenone, phenothiazine, and DDT.

Cited by 9 publications

References 15 publications

The Persistence and Fate of DDT on Foliage. I.—The Influence of Plant Wax on the Toxicity and Persistence of Deposits of DDT Crystals

The Persistence and Fate of DDT on Foliage. I.—The Influence of Plant Wax on the Toxicity and Persistence of Deposits of DDT Crystals

Título en español.

Particle Size of Insecticidal Suspensions and Their Contact Toxicity Iv. Mechanisms of Action of Different‐sized Particles

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