Plant uptake, persistence, and insecticidal efficiency of three systemic insecticides (phorate, demeton, and dimethoate) were studied on cotton plants in the greenhouse. Materials were applied as seed treatments and as granulated formulations (on attaclay and vermiculite carriers) at time of planting and to established plants. Pour soil types were included: fine sandy loam (Moreno, pH 7.1); loamy fine sand (Indio, pH 9.1); clay loam (Imperial Valley, pH 8.1); and silty loam (San Marcos, pH 6). All seed treatments retarded germination, especially in the lighter soils; soil treatments at time of planting produced the same trend but less severely. Phytotoxicity was most pronounced with seed treatments; the effects from insecticides on vermiculite granules applied at planting were more severe than from those on clay granules. Plant injury was more severe in lighter soils. The injury caused by dimethoate seed treatment was the most severe, with phorate- and demeton-caused injury following in order of decreasing intensity. Granulated formulations applied to the soil on established plants gave typical systemic burn on the leaf margins that was most severe on dimethoatetreated plants. Bioassay with spider mites, Tetranychus cinnabarinus (Boisd.), revealed highest initial concentrations of toxicants in the plants grown from treated seed. The light soils allowed the fastest uptake of toxicants and the highest levels of toxicant concentration within the plants. Vermiculite granules released toxicants more rapidly than clay granules but residual activity did not persist as long. Granulated dimethoate reached lethal concentrations in the plant most rapidly but lost its effect most quickly; phorate showed the greatest persistence. Soil pH did not prove to be a major factor in toxicant uptake, but soil texture was important, the lighter, sandy soils allowing materials to be absorbed by plant roots more rapidly. Leaching experiments demonstrated the faster movement of the systemic insecticides in sandy soils. Similar experiments demonstrated a quicker release of tOll.1cantsfrom vermiculite than from clay granules.
Document Type: Research Article
Publication date: June 1, 1961
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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.