Asulam

Asulam is a herbicide used primarily for the control of bracken. It is a systemic herbicide, absorbed by the foliage and roots, and transported throughout the plant. Asulam is particularly effective against bracken due to its selective nature, causing minimal damage to grasses and other desired plants.

Chemical Structure and Properties

Asulam is a sulfonamide herbicide, with the chemical formula C8H9NO5S. It is a white crystalline solid at room temperature, with a melting point of 158-160°C. It is soluble in water and most organic solvents. Asulam is non-volatile and has a low potential for leaching into groundwater.

Mode of Action

Asulam acts by inhibiting the enzyme dihydropteroate synthase (DHPS), which is involved in the synthesis of folate in plants. Folate is essential for the production of DNA and proteins, and its depletion leads to the death of the plant.

Use and Application

Asulam is applied as a foliar spray during the growing season, typically in late summer when bracken is fully grown but before it starts to die back. It can also be applied as a soil treatment in the early spring before bracken emerges.

Safety and Environmental Impact

Asulam is of low toxicity to humans and animals. However, it can cause eye irritation and skin sensitization in some individuals. It is also toxic to some species of aquatic organisms. Asulam is not persistent in the environment and is rapidly degraded by soil microorganisms.

Regulation

In the European Union, the use of asulam was banned in 2012 due to concerns about its potential impact on non-target organisms. However, emergency authorizations have been granted in the UK for the control of bracken in certain situations.

See Also

• Herbicide
• Sulfonamide
• Dihydropteroate synthase
• Folate