MCPA-sodium is a selective endogenous transduction hormone herbicide of phenoxyacetic acid, which can damage the conduction tissues of dicotyledonous plants, interfere with the growth and development, distort the stem and leaf, expand and thicken the stem base or crack.The volatility and action rate were lower and slower than 2, 4-d. MCPA-sodium was very sensitive to the seedling stage of gramineous plants, and the resistance gradually increased after the 3-4 leaf stage, the highest at the end of tiller stage, and the sensitivity increased again at the stage of young panicle differentiation.When the temperature is lower than 18℃, the effect is obviously worse, which is not good for unexcavated weeds.Usually 30 to 60 grams per acre (active ingredient).Strictly prohibited for dicotyledon crops!