Studies were conducted in the greenhouse to determine the relative effect of phorate, Di-Syston® (O,O-diethyl S-2-(ethylthio) ethyl phosphorodithioate), and SB-3562 (dimethyl 1- (dimethylcarbamoyl)-l-propen-2-yl phosphate) on the germination of wheat when applied as a seed treatment. Extensive testing of phorate was carried out in a factorial experiment using rates from 0.18 to 1.5 pounds of active toxicant per 100 pounds of seed, with six fungicides and five stickers. Both phorate and SD-3562 were seriously toxic to wheat seed, with the latter being most toxic under the test conditions. Di- Syston did not significantly reduce seed viability with rates as high as 1.5 pounds per 100 pounds of seed. The data suggest interactions between certain stickers and fungicides to reduce phytotoxicity of phorate. Another interaction between phorate and a sticker composed of 3 parts dextrin, 1.5 parts sorbitol, and 0.5 part water to lessen the toxic effect of the insecticide to the seed was apparent. Phytotoxic effects of phorate on seed viability increased as the interval between treatment and seeding was prolonged. However, data indicate that this was largely due to the sticker used to apply the phorate. This effect was slight with the sticker mentioned above, but very severe with another sticker composed of 1.4 parts rice oil, 2 parts sorbitol, and 0.6 part dextrin. Phytotoxic effects are apparently reduced by the interaction of phorate with the fungicide and sticker. The adverse effects of phorate when applied as a seed treatment to wheat at the rates most likely to be used in the field, and with the use of a suitable sticker and fungicide, should be greatly reduced.
Document Type: Research Article
Publication date: August 1, 1960
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