有機燐製剤に関する研究

VI. メチルパラチオン粉剤における安定剤の殺虫力に及ぼす影響について

抄録

In the previous reports, the authors have studied the stabilization of organophosphorus insecticides and have reported that the surface acidity ofmineral carriers effects the stability of methyl parathion dust formulation with stabilizers, such as polyoxyethylene alkyl ether (PAE), polyoxyethylene dialkyl ether etc. The crop field tests and laboratory experiments were made in order to observe the effect of stabilizers on the insecticidal activity in methy parathion dust formulations. In the laboratory experiment, Callosobruchus chinensis LINNÉ and Allantus luctifer SMITH were used as test insects. In the crop field test, the first and second broods of the rice stem borer, Chilo suppressalis WALKER were used as test insects. Methyl parathion dust formulations with clay, clay plus talc (1:1), clay plus talc (3:1) and stabilizers were used as test insecticides (Tables 1, 2). Stabilizers used were PAE, alkyl naphthalene sulfonic acid salt (ANS), #0 fatty acid, and cuttlefish oil.
The results of biological assay were shown in Tables 2, 4, 7 and 8, and these values, when transfered into probit unite and plotted against the time on logarithmic scale, revealed linear regressions in the condition under which the experiment was carried out (Tables 3, 5, 6). In the case of methyl parathion dust formulations with stabilizer, the effect on the insecticidal activity depends upon the sort of mineral carriers and stabilizers. When clay only was used as a diluent, PAE 0.5% as a stabilizer increased rather than obstructed the insecticidal activity of methyl parathion dust formulations.
When clay plus talc (1:1) was used as a diluent, cuttle fish oil as a stabilizer obstructed the insecticidal activity and it was inferior to methyl parathion dust formulation without stabilizer. ANS had no connection with any sort of mineral carrier and rarely obstructed the insecticidal activity. Methyl parathion dust formulations with clay plus talc (3:1) were scarcely influenced by stabilizers and the result obtained by Bliss probit method is insignificant.
But perhaps, the influence of talc brings about the tendency that dust formulations with PAE are slightly inferior to that with #0 fatty acid on ANS in the insecticidal activity.
When talc is used as a diluent, stabilizing effect by compounds of PAE series is not remarkable, as the authors have explained in the previous reports. Though we could not ascertain the relationship between the quantity of stabilizer and insecticidal activity in this test, the result obtained by the crop field test shows, evidently that the insecticidal activity of dust formulations with 0.5% stabilizer is superior to that of dust formulations with 2.0% stabilizer and a proper quantity of stabilizer is approximately 0.5-0.7%.
Consequently, in the search of a stabilizer for methyl parathion dust formulation use, we should carry out the biological assay in company with the chemical test of stability, sufficiently to determine the proper quantity of stabilizer, stabilizing effect, and the degree of obstructive action.