Insecticides Phorate Research Articles

Effects of Various Soil Types and Methods of Application upon Uptake of Three Systemic Insecticides by Cotton Plants in the Greenhouse1

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 toxicants from vermiculite than from clay granules.

Systemic Insecticides as Soil Treatments for Control of the Mimosa Webworm, Homadaula albizziae1

The mimosa webworm, Homadaula albizziae Clarke, was found in Kentucky by 1950, and is now statewide in distribution. Most of its damage is directed at ornamental plantings of mimosa and locust. Experimental work in control began in 1957. In August, 60 moraine locust trees were sprayed once with dieldrin, malathion or toxaphene emulsion concentrates, Toxaphene was the most effective measured by larval counts made 6 days after application, but by September it was difficult to distinguish treated from untreated trees. In 1950, the systemic insecticides phorate and demeton in one early season application were tested on locust, using three techniques. Trunk implantation of concentrates, applied directly or encapsulated into holes bored into the trunk gave variable results. Soil injections applied with n hydraulic sprayer using 20 gallons of spray mixture in four to six probes within 3 feet of the tree trunk were effective when the dose was 80 grams of material per 3-inch tree, Foliar applications of demeton and phorate were effective, but. one application was not sufficient to keep the trees free of infestation for the whole season. In 1960, granulated Di-Syston® ( O,O -diethyt S -2-(ethylthio) ethyl phosphorodithioate) and phorate applied to the soil and 10-foot circle around the tree, worked lightly into the soil and then watered, gave effective control, as did the emulsion concentrate of phorate sprinkled around the tree in a 10-foot circle, Control of three generations of this insect was achieved, An abundant supply of water is probably required for effectiveness, Placing thc materials into holes in the ground under the limbspread proved ineffective. Spray treatments alone or combined with granules did not add to the effectiveness, Tests of foliage 5 months after application of Di-Syston and phorate to soil gave strong cholinesterase inhibition.