| Abstract: | Analysis of samples of seeds, mostly wheat, treated commercially with insecticides and fungicides showed that many carried much less than the theoretical dose, some less than one-tenth. The average loadings of seeds treated with dry powder formulations were nearly always small, but the distribution of insecticide between seeds was fairly uniform. The average loading of seeds treated with liquid formulations was closer to the target, but the distribution was irregular, most of the seeds carrying little insecticide and a few seeds amounts large enough to be phytotoxic. Insecticides applied as dry powders do not adhere strongly to the seeds, but they remain in association with seeds contained and carried in bags. Applied as liquids, insecticides are difficult to remove from seeds. The ratio of insecticide to fungicide on seeds dressed with powders containing both usually resembled the ratio in the original powder. With liquid seed dressings of insecticide and fungicide applied separately in different formulations, the ratio of insecticide to fungicide often differed widely from the theoretical. The average loading of fungicide was close to the target, but the average amount of insecticide was often much less. With either wet or dry dressings, the amount of pesticide on seeds was consistently greater from some merchants than from others. This was independent of the machinery used. Loadings were not consistently affected by type of seed-dressing machinery or formulation, stage of operation, weather or variety of seed. |
