Crops Where Paraquat is Used
Paraquat is a fast-acting, non-selective herbicide used to control unwanted vegetation in many commercial agricultural settings. It is a "restricted-use pesticide," meaning it can only be purchased and applied by licensed individuals. Its application targets green plant tissue and, because it binds strongly to soil, it has very little residual activity after application. This allows for planting to occur relatively soon after treatment.
Grains and Feed Crops
Grains and animal feed crops are among the most common applications for paraquat. It is often used to control weeds in fields before planting or after the harvest of specific crops.
- Corn: Used for general weed control.
- Wheat: Used to control weeds in wheat fields.
- Soy: Applied for weed management, particularly before planting soybeans.
- Rice: Used for weed control in rice paddies before the crop is fully established.
Fruits and Vegetables
Orchards and vineyards use paraquat to manage weeds between rows, as it does not penetrate bark or affect the central plant. It can also be used on specific fruit and vegetable crops.
- Grapes: Used in vineyards for weed management.
- Citrus Trees: Applied in citrus groves to control weeds around the trees.
- Strawberries: A crop on which paraquat is sprayed.
- Pears: Used in pear orchards for weed control.
- Artichokes: Another vegetable crop mentioned in connection with paraquat use.
- Sweet Potatoes: Applied to control weeds.
- Potatoes: Used as a desiccant to dry out the potato foliage before harvest.
Nuts and Other Commercial Crops
In addition to fruits and vegetables, paraquat is also widely applied to certain nuts and other commercial agricultural products.
- Almonds: Used for weed control in almond orchards.
- Peanuts: Applied for weed control in peanut fields.
- Cotton: Used as a desiccant on cotton plants to help prepare them for harvest.
- Garlic: A crop on which paraquat is used for weed control.
Why is Paraquat Used on Food?
The primary reason for using paraquat in agriculture is its effectiveness as a non-selective, contact herbicide. It is particularly valuable in specific agricultural practices where weed control is challenging.
- Weed Control: Paraquat kills weeds on contact, preventing competition for nutrients and water with crops.
- Desiccation: For certain crops like potatoes and cotton, it is used as a desiccant to dry the plant leaves and stems before harvest. This makes the harvesting process more efficient.
- No-Till Farming: Paraquat's lack of residual soil activity makes it useful for no-till or minimum-tillage farming systems, which help prevent soil erosion and preserve soil structure.
- Glyphosate-Resistant Weeds: As some weeds develop resistance to other herbicides like glyphosate, paraquat is sometimes used as an alternative or in conjunction with other chemicals to combat resistant vegetation.
How Regulations Impact Paraquat Use
Due to its high toxicity, paraquat is one of the most highly regulated pesticides in the United States. Numerous international bodies have also taken action to restrict or ban its use, leading to ongoing global debate.
In the US, the Environmental Protection Agency (EPA) designated paraquat a "restricted-use pesticide" in 1978 and has since added further safety requirements. Only certified applicators are legally permitted to handle and apply the product. Strict training requirements, special packaging, and storage mandates are in place to minimize the risk of exposure, especially accidental ingestion, which is often fatal. Many countries, including those in the European Union, have banned paraquat altogether. Despite this, it continues to be legally used in many nations, including the US, Brazil, and India.
The Role of Testing and Residues
Even with regulations, there is concern about potential paraquat residues remaining in food products. Studies have focused on detecting and monitoring these residues. One study on soya products, for instance, found paraquat residues in a significant portion of samples, some exceeding EU maximum residue levels. Paraquat can be absorbed by the soil, and a study on wheat grains found alarming residue concentrations, which were linked to soil contamination. These findings underscore the importance of robust monitoring programs and adherence to regulations to limit contamination risks. For more detailed information on safety protocols for certified applicators, consult the US EPA worker safety guidelines.
A Comparison of Paraquat's Uses in Agriculture
| Application Method | Purpose | Crop Examples | Key Benefit | Associated Risk |
|---|---|---|---|---|
| Pre-Planting Weed Control | Kills existing weeds before new crops are planted. | Corn, Soy, Wheat | Allows for effective weed management in low-tillage farming. | Potential for drift and environmental contamination. |
| Pre-Harvest Desiccation | Dries out plant foliage to facilitate mechanical harvesting. | Potatoes, Cotton | Speeds up the harvest process and increases efficiency. | Residue can remain on the plant matter and contaminate food/feed. |
| Vineyard/Orchard Weed Control | Eliminates weeds between rows and around established trees/vines. | Grapes, Citrus, Almonds | Kills weeds without harming the main woody plant. | Potential for drift to other plants or water sources. |
Conclusion: The Continued Debate Over Paraquat Use
Paraquat is a potent and effective tool for weed control and desiccation in modern agriculture, used on a wide range of food crops and animal feed. Its utility in no-till farming and combating resistant weeds is a key driver of its continued use in some countries. However, its high toxicity and links to severe health problems, like Parkinson's disease for exposed applicators, have led to it being banned in many other nations. The stringent "restricted-use" status in the US, along with ongoing monitoring of residues, aims to mitigate public health risks. Ultimately, the debate continues over whether its agricultural benefits outweigh the significant health and environmental concerns associated with its application on food production.
