Efficiency of Granulated Insecticides Influenced by Solvents Used for Impregnation1,2

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In mosquito larviciding and other aquatic insect pest control programs, quick kill of the larvae of the insects before they can change into pupae and adults is necessary. The use of granulated insecticides in such control measures has great possibilities, provided the formulations are capable of releasing a large portion of the toxicants within 24 hours after treatment. Formulations that release the toxicant slower are not desirable except possibly in certain prelarviciding treatments for mosquito control.

The efficiency of 44 petroleum solvents was investigated in a study of the various physical and chemical factors influencing and regulating the rate and magnitude of release of toxicants from granular formulations. The solvents had a wide range of physical and chemical properties. A 2% parathion impregnated formulation was prepared using 30/60 mesh, AA-LVM attapulgite granules. The granules were dropped into water and the rate of parathion release was determined by bioassaying aliquots of the treated water against fourth-instar larvae of Culex quinquefaseiatus Say.

The rate and magnitude of release for almost all of the petroleum solvents (aromatics, paraffins, and naphthenes) were found to be affected to a great extent by the flash point, minimum and maximum boiling points, distillation range and evaporation rate of these solvents. It was further noted that there existed an inverse relationship between the rate and extent of release and these physical characteristics of the solvents. With an increase in the values of these properties there was a tendency for slower releases and vice versa. A simple formula has been presented which illustrates this relationship, as follows:


Where REI is relative efficiency index, FP is flash point, IBP is initial boiling point, and EP is end point. Solvents with higher REI values generally resulted in formulations releasing parathion slower than those prepared with solvents having lower REI values. Solvents with extreme distillation properties are easily separated by this formula.

By selecting suitable solvents to impregnate granules with the toxicant solution, it is possible to prepare a wide array of granular formulations which will give either slow, intermediate, or rapid release of the toxicant depending on the particular solvent. The studies reported are aimed at gross separation of petroleum solvents into highly efficient, less efficient and inefficient solvents which might be used for impregnation of granulll1' carriers with parathion.

Document Type: Research Article

Publication date: October 1, 1960

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  • Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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