Introduction
2,4-Dichlorophenoxyacetic acid, also known as 2,4-D is an organic compound of the chemical formula C8H6Cl2O3 that is commonly used as a herbicide to kill broadleaf weeds on plants. It is a chemical analogue of auxin that is used as supplements in various plant research laboratories and causes uncontrollable and lethal growth in plants.
It is one of the oldest herbicides being used since the time of world war II. It acts as a selective herbicide that kills only dicots without affecting grasses and monocots.
Chemical Properties
- It is a halogenated phenoxy compound that contains two chlorine atoms that are substituted at the 2nd and 4th position along with an acetic acid side chain.
- In its most refined form, it appears as a white powder with no characteristic odour.
- It causes no corrosion when kept on a surface or container.
Discovery
The discovery of 2,4-D was the work of groups of scientists involved from different countries during World War II. During wartime, it was used with 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) to obtain a compound called Agent Orange. But soon this was discontinued because of serious health concerns caused by Agent Orange.
2,4-D was commercially released in 1946 and has since become the most commonly used herbicide all over the world.
Mode of Action
As stated by the Environmental Protection Agency of the USA, 2,4-D kills the plants in three ways:
- By altering the plasticity of the cell walls
- Increasing the production of ethylene in plants
- And, influencing the protein synthesis.
When applied in recommended doses, 2,4-D causes uncontrolled growth in plants—leaves wither, stems curl over and eventually the plant dies. It gets absorbed through the leaves and gets transported to the meristem of the plant. Conversely, at lower doses, the compound mimics auxin and promotes plant growth and development.
Applications
- It is used to control weeds in forestry for trunk injection, stump treatment, and for the selective control of brush in conifer forests.
- It is used in lawn care and turf practices to get rid of dandelions, clover, plantain and chickweed.
- It also finds its use in controlling aquatic weeds that may otherwise interfere with fishing, boating, swimming and hydroelectric equipment.
- It is used by the government to stop the invasion of non-native weeds at native places.
- It can be used to control poisonous weeds such as poison ivy and poison oak.
How to Apply 2,4-D?
2,4 D can be applied in a variety of ways. The acid itself is difficult to dissolve in water. To overcome this problem, it is first dissolved in alcohol then it can be dissolved in water. It can also be dissolved in some other organic solvent such as polyethylene glycol.
The salts obtained with sodium and ammonium have also been proved to be as effective as the acid forms. It can also be used as emulsions in the form of esters that are soluble in oils. It has also been used in aerosol form by dissolving in dimethyl ether.
When used as a water spray herbicide, usually one part of the active ingredient is mixed with 1000 parts of water by weight.
Advantages
- It is easy to manufacture.
- The manufacturing cost is very low and hence can be used widely in commercial applications.
- It is widely used as a grass herbicide to kill dicot plant tissues.
- It has also been seen to promote rooting in plant cuttings, fastening the ripening of fruits and reducing scalding on fruits in storage.
- It is used as a hormonal supplement in place of indole acetic acid (auxin) in plant cell culture.
Disadvantages
- Ingestion above a certain concentration can cause poisoning in humans and can induce coma, abdominal pain, vomiting and hypotonia.
- Men working with the compound were often found to have differently shaped sperm and infertility issues.
- It has been classified as a carcinogenic compound.
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Frequently Asked Questions
Is 2,4-D the same as Roundup?
No, Roundup is the commercial name for glyphosate-based herbicide, while 2,4-D is a halogenated phenoxy compound.
Why does 2,4-D not affect monocot plants?
The effect of 2,4-D on monocots is not clear but one reason could be that the monocots have limited translocation of auxin due to their vascular system being different from the dicots. Thus, the 2,4-D is not that well absorbed in monocots.
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