Responses of the rice plant to different formulations and methods of application of 2,4-D, MCP, and 2,4,5-T

The research described in this paper is a continuation of studies carried on during the past four years on the effects of the phenoxyacetic acid herbicides on rice and on weeds of rice fields. Injury to rice from 2,4-D sprays is fairly common; injury to surrounding sensitive crops from spray drift has also been experienced. The study described here compared the effects on rice and on weeds of 2,4-D, MCP, and 2,4,5-T applied to the water on rice cultures and applied as pellets to rice cultures. Applied to the water in aqueous solution, the most deleterious effects on the rice plants occurred when the rice seed was sown on top of the soil, as contrasted with being drilled into the soil; when the rice was treated at early stages of growth; when dosage was high; and when 2,4-D was used. Treatments with pellets caused intense aberrations in rice and aquatic weeds when plants were young, when dosage was high, and when 2,4-D was used. MCP was less injurious to rice, yet it killed aquatic weeds. The 2,4,5-T treatments were ineffective against weeds. At equivalent dosage, pellets were more selective than were aqueous solutions. Pellets effectively controlled aquatic weeds in rice without injury to the latter under greenhouse conditions.