2,4-D (U46 D) 72%
Trade Name: U46 D
Group: Phenoxy Carboxylic Acid
Pre-harvest Interval: 7 days
Antidote: Gastric lavage, activated charcoal, sedatives

Type: Hormonal, systemic, selective herbicide from the phenoxyacetic acid group
Soil Persistence (Half-life): 7 days; typically, at doses of 1–1.5 L/ha, less than one month

Mode of Action

• Mechanism: Inactivates the enzyme indole-3-acetic acid oxidase, increasing auxin concentrations in plant tissues

• Absorption & Translocation: Salt forms are absorbed via roots; ester forms via aerial parts. Moves through the symplast and accumulates in meristematic tissues

• Symptoms in Plants: Disruption of growth, twisting of aerial parts, swelling of petioles and stems, abnormal elongation, leaf drooping, and eventual plant death

Application: Applied as a foliar spray. Water should be drained from the fields before spraying and avoided for 24 hours after treatment.

Usage Management

• Perennial weeds: Apply during fallow periods, after wheat harvest, or when perennials begin flowering. For wheat, it can be used during the grain hardening stage and suitable vegetative stage for perennials. Avoid use in cotton fields.

• Spot spraying: For perennial weeds, spray 1% solution with back sprayers. Adding 10 kg/ha ammonium sulfate enhances efficacy.

• Reduced doses with repeated applications (every 7–10 days) can improve control.

• Broadleaf weeds: Usually applied alone or mixed with herbicides like atrazine.

• Maximum spray frequency: Once per year in crops, twice per year in forest areas, 2–3 times per year in pastures or lawns.

• Avoid application in newly seeded grass or on crops under stress (cold, drought). Do not apply if frost is expected.

• Rainfall within six hours of spraying does not reduce efficacy due to rapid absorption.

Recommended Application

Compatibility and Notes

• Use proper nozzle and pressure to ensure coarse droplets and minimize drift. Recommended spray volumes: 300 L/ha for backpack sprayers, 200 L/ha for tractor sprayers, 20 L/ha for aerial application.

• Low concentrations are active; high concentrations may damage recommended crops.

• Do not use on newly seeded legumes, cotton, sugar beet, tomato, potato, grape, ornamentals, or fruit trees—these are sensitive to 2,4-D MCPA.

• Avoid spraying during or immediately before rainfall.

• Keep livestock away for at least 2 weeks until weeds die and odor dissipates.

• Ideal spray temperature: 10–30 °C. Do not apply below 5 °C or when frost is expected.

• Conduct compatibility tests before mixing with other chemicals.

• Only use under plant protection specialist supervision and for recommended crops/weeds.