Studies on the Soil Application of the Insecticides : III. Effectiveness of the Systemic Organophosphates against the Large 28-spotted Lady Beetle on Potatoes

Abstract

The band application of 5 % Di-Syston granules at 6kg per 10a in the seed furrow at planting time revealed excellent control of the large 28-spotted lady beetle, Epilachna vigintioctomaculata MOTSCHULSKY, throughout all of the stages of potato growth. This effect was considered to be owing to the death of the greater part of both larvae and adults of the species, within one or two days after the benining of feeding by the systemic toxicants absorbed through the root. The present method was about same or greater in effectiveness to the usual pest control method with two sprayings of 0.05% MEP or DDT emulsions and others in the period from the stage of flower-bud formation to the flowering time. The application of the granules in fertilizer bands beneath the seed pieces of potato had more or less poor effects on the control of pest compared with the above method. Di-Syston granules was more effective than PSP-204 granules in the tested dosages. About 6kg per 10a seemed to be the suitable dosage for controlling major insect pests including the large 28-spotted lady beetle and for the good yields of potato tubers. No detrimental insecticidal residues on the harvested potato tubers was recognized in the practical application of dosages below 6 or 10kg of Di-Syston or PSP-204 granules.