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A statistical method for testing mixtures of chemicals based on a model for independent joint action with no correlation in susceptibility is described. Antagonism (significantly less mortality than predicted by the model), synergism (significantly greater mortality than predicted), and independence (no significant difference in mortality) may be identified at one response level or over a range of levels by this method. Each of three pyrethroids (decamethrin, fenvalerate, and permethrin) was tested in a 1:10 mixture with each of four carbamates (aminocarb, carbaryl, methomyl, thiodicarb) and five organophosphorous insecticides (acephate, chlorpyrifos, fenitrothion, malathion, phosmet) by topical application to 6th-instar Choristoneura occidentalis Freeman. Co-toxicity ratios (LC", predicted -;.-LC", observed) ranged from 0.5 to 7.3 but were not reliable indicators of the type of joint action occurring because response lines of mixture components were not generally parallel. By the criterion of synergism in the upper (>50% mortality) concentration range, mixtures of fenvalerate with aminocarb, carbaryl, methomyl, thiodicarb, acephate, fenitrothion, or phosmet; decamethrin with acephate, carbaryl chlorpyrifos, or fenitrothion; and permethrin with carbaryl, methomyl, or thiodicarb appear to merit testing in more intensive bioassays involving spray applications to insects on foliage.
Document Type: Research Article
Publication date: February 1, 1984
More about this publication?
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.