2,4-D

2,4-Dichlorophenoxyacetic acid (commonly known as 2,4-D) is a widely used systemic herbicide that selectively kills most broadleaf weeds by causing uncontrolled growth in them, while leaving most grasses such as cereals, lawn turf, and grassland relatively unaffected. It is one of the oldest and most widely available herbicides in the world, having been first introduced in the 1940s.

History

2,4-D was developed during World War II and was one of the first herbicides to be commercially produced. It was discovered by a team of British scientists led by William Templeman. The compound was introduced to the market in 1945 and quickly became popular due to its effectiveness and low cost.

Chemical Properties

2,4-D is a chlorinated phenoxy compound. Its chemical formula is C₈H₆Cl₂O₃, and it is a white crystalline solid at room temperature. It is soluble in water and can be formulated as an amine salt, ester, or acid.

Mechanism of Action

2,4-D acts as a synthetic auxin, which is a type of plant hormone. It mimics the action of natural auxins, causing uncontrolled and disorganized growth in susceptible plants. This leads to the death of the plant due to the disruption of normal growth processes.

Uses

2,4-D is used in agriculture, forestry, and urban areas to control broadleaf weeds. It is commonly applied to:

• Cereal crops such as wheat, corn, and rice
• Pastures and rangelands
• Lawns and turf
• Aquatic weed control

Safety and Environmental Impact

2,4-D is considered to have low toxicity to humans and animals when used according to label directions. However, it can cause irritation to the skin and eyes. There is ongoing research into its potential environmental impacts, particularly concerning its effects on non-target plant species and aquatic ecosystems.

Regulation

2,4-D is regulated by various governmental agencies around the world, including the Environmental Protection Agency (EPA) in the United States. It is approved for use in many countries, but its application is subject to specific guidelines to minimize environmental and health risks.

Controversy

There has been some controversy surrounding 2,4-D due to its association with Agent Orange, a defoliant used during the Vietnam War that contained a mixture of 2,4-D and 2,4,5-T. Concerns about dioxin contamination in 2,4,5-T led to its ban, but 2,4-D continues to be used widely.

Also see

• Herbicide
• Auxin
• Agent Orange
• Pesticide regulation