Introduction
2,4-D (C₈H₆Cl₂O₃) is a synthetic auxin (HRAC Group 4) that disrupts plant growth regulation in broadleaf weeds, causing uncontrolled cell division and death. It is selective in grasses, allowing post-emergence control in cereals and turf.
History & Development
Commercialized in the 1940s, 2,4-D ushered in selective chemical weed control. Various salt and ester formulations have been developed to balance volatility, rainfastness, and crop safety. The recent 2,4-D choline formulation improved drift/volatility characteristics for use with 2,4-D-tolerant crop traits.
Use Patterns
- Crops: Wheat, barley, oats (post-emergence), pasture/rangeland, turf, fallow fields.
- Spectrum: Dandelion, plantain, thistles, mustards, many broadleaves; limited on grasses.
- Formulation choice: Esters (more active in cool weather, higher volatility); amines/choline (lower volatility, better stewardship).
Stewardship & Risk
- Drift/volatility: Sensitive dicots (tomato, grapes, cotton varieties) can be injured; follow label-mandated buffers, nozzle/pressure specs, and temperature cutoffs.
- Resistance: Documented in several species; manage via tank mixes (e.g., with ALS, HPPD, PPO inhibitors) and cultural practices.
Market & Outlook
2,4-D remains a workhorse for cereals and turf for cost-effective broadleaf control. Trait stacks (2,4-D-tolerant crops) extend utility but heighten stewardship expectations. Expect continued use with tighter application standards and more precision tech (boom height sensors, drift-reducing nozzles).
