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During the late summer of 1956 an increasing number of failures were reported in alfalfa fields where parathion and malathion were used to combat the spotted alfalfa aphid, Therioaphis maculate (Buckton), in southern California. A survey of the troubled area strongly indicated the presence of a resistant strain of aphids. Field tests showed that the aphid has developed a low degree of resistance to parathion and Trithion in localized areas. In one test, malathion, Phosdrin, and demeton (Systox) applied at 9.1, 0.7, and 0.9 ounces per acre, respectively, gave only mediocre control. These same dosages gave excellent control of susceptible aphid populations. Laboratory studies showed that the aphid had developed approximately 4-fold resistance to parathion residues. If time of exposure to mortality is considered, the degree of resistance is probably even greater. Resistant aphids continued reproduction when exposed to the toxic ant, and many of their young survived. Reproduction in nonresistant aphids was markedly reduced, and the young died. The developmental pattern of resistance in parthenogenetic species docs not progress in the same manner as in multivoltine bisexual species. Resistance probably arose through mutation after the aphid arrived in North America.
Document Type: Research Article
Publication date: June 1, 1958
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.