Herbicidal Properties of 2,4-Dichlorophenoxyacetic Acid Applied in Dusts Containing Hygroscopic Agents

1. 2,4-Dichlorophenoxyacetic acid was applied in different concentrations (0.5, 1.0, 2.5, 5.0, and 10.0%) in dust carriers, at the rate of 4 pounds per 1000 square feet, to Kentucky bluegrass (Poa pratensis) and white clover (Trifolium repens) growing in a mixed stand in greenhouse flats. The 10.0% dusts were also tested on heal-all (Prunella vulgaris) and lawn pennywort (Hydrocotyle rotundifolia) in flats and on narrow-leaved plantain (Plantago lanceolata) growing in 3-inch clay pots in a greenhouse. 2. Comparison of Pyrax, fuller's earth, and Cherokee Clay as diluents or dust carriers at each of the concentrations indicated that there was no marked difference among them on the basis of the plant responses observed. 3. Complete eradication of clover from bluegrass turf was obtained by applications of dust containing 10.0% of the acid, but the bluegrass was severely injured and recovered only slowly. Almost complete eradication (99%) was obtained by application of dust containing 5.0% of the acid, and the...