All pesticides are required to seek registration from appropriate authorities in the country in which they will be used.
In the United States, the Environmental Protection Agency (EPA) is responsible for regulating pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA).
A pesticide can only be used legally according to the directions on the label that is included at the time of the sale of the pesticide.
The purpose of the label is "to provide clear directions for effective product performance while minimizing risks to human health and the environment".
A label is a legally binding document that mandates how the pesticide can and must be used and failure to follow the label as written when using the pesticide is a federal offense.

Within the European Union, a 2-tiered approach is used for the approval and authorisation of pesticides.
Firstly, before a formulated product can be developed for market, the active substance must be approved for the European Union.
After this has been achieved, authorisation for the specific product must be sought from every Member State that the applicant wants to sell it to.
Afterwards, there is a monitoring programme to make sure the pesticide residues in food are below the limits set by the European Food Safety Authority.
Although diquat was used in many European countries from the 1960s, an EU directive has removed its approval for any use, effective from 12 October 2018.

Diquat is an unusual herbicide because it is often not used for weed control but is instead applied directly on mature crops.
This causes desiccation, making the crop easier to harvest, particularly with mechanised equipment.
The advantage to the farmer can be to advance the harvesting date, reduce the time taken to harvest and, in the case of seed crops, reduce the moisture content of the seed and increase its useful yield.
Farmers can act in their best economic interest: the value of these benefits can be estimated and the total cost of using the herbicide, including the cost, for example of aerial spraying, informs the decision to purchase.
This cost-benefit  analysis by the end user sets a maximum price which the supplier can demand.
When used as a conventional herbicide for weed control, diquat must be applied after the weeds have emerged since it is only effective on contact with green tissue.
In this use it is fast-acting in sunlight and more effective on broadleaved weeds than grasses.
Mixing of diquat with other herbicides is also feasible.
The estimated annual use of diquat in US agriculture is mapped by the US Geological Service.

Beyond agriculture, diquat is also used to control invasive species such as submerged aquatic vegetation in the California Delta.
Because California public drinking water is drawn through the delta as part of the California State Water Project, trace amounts of this pesticide are in much of the state's water supply.
All pesticides are required to seek registration from appropriate authorities in the country in which they will be used. In the United States, the Environmental Protection Agency (EPA) is responsible for regulating pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Food Quality Protection Act (FQPA). A pesticide can only be used legally according to the directions on the label that is included at the time of the sale of the pesticide. The purpose of the label is "to provide clear directions for effective product performance while minimizing risks to human health and the environment". A label is a legally binding document that mandates how the pesticide can and must be used and failure to follow the label as written when using the pesticide is a federal offense.
Within the European Union, a 2-tiered approach is used for the approval and authorisation of pesticides. Firstly, before a formulated product can be developed for market, the active substance must be approved for the European Union. After this has been achieved, authorisation for the specific product must be sought from every Member State that the applicant wants to sell it to. Afterwards, there is a monitoring programme to make sure the pesticide residues in food are below the limits set by the European Food Safety Authority. Although diquat was used in many European countries from the 1960s, an EU directive has removed its approval for any use, effective from 12 October 2018.
Diquat is an unusual herbicide because it is often not used for weed control but is instead applied directly on mature crops. This causes desiccation, making the crop easier to harvest, particularly with mechanised equipment. The advantage to the farmer can be to advance the harvesting date, reduce the time taken to harvest and, in the case of seed crops, reduce the moisture content of the seed and increase its useful yield. Farmers can act in their best economic interest: the value of these benefits can be estimated and the total cost of using the herbicide, including the cost, for example of aerial spraying, informs the decision to purchase. This cost-benefit  analysis by the end user sets a maximum price which the supplier can demand. When used as a conventional herbicide for weed control, diquat must be applied after the weeds have emerged since it is only effective on contact with green tissue. In this use it is fast-acting in sunlight and more effective on broadleaved weeds than grasses. Mixing of diquat with other herbicides is also feasible. The estimated annual use of diquat in US agriculture is mapped by the US Geological Service.
Beyond agriculture, diquat is also used to control invasive species such as submerged aquatic vegetation in the California Delta. Because California public drinking water is drawn through the delta as part of the California State Water Project, trace amounts of this pesticide are in much of the state's water supply.
Diquat