North America

Think of citrus and you probably think of freshly squeezed orange juice, and a grapefruit for breakfast, or later, a slice of lemon in your G and T. But have you heard of the many other citrus fruit that make-up this vast family which collectively are the number one fruit in international trade? Try calamondins, citrons, pomelos or ugli fruit sometime.
One third of global citrus production is for juice and this is the area of increasing consumption rather than fresh fruit. More than 80% of citrus going for juicing are oranges, the rest are mostly grapefruit. However, the conveniently small (‘lunch-box size’) and easy-peel, often seedless, tangerines, mandarins, clementines and satsumas have risen in popularity in recent years.
Paraquat is an essential tool in citrus
Paraquat is a broad spectrum herbicide. Its mode of action is to inhibit photosynthesis. This process is essential to plants and means that paraquat destroys all green tissue.
Although it is termed ‘non-selective’, paraquat is safe to citrus trees for several reasons. First, paraquat is immobilized on contact with the soil meaning that it cannot move to roots and be taken up into plants.
You can read more about paraquat’s unique soil properties here.
Articles in this section are about specific examples of how paraquat is being used and new uses explored in sustainable cropping systems.
The case studies show how farmers, their families and their land can benefit by farming with paraquat; and how this enables them to grow better crops.
Paraquat is one of the most widely used herbicides in the world, marketed globally under the brand name Gramoxone by Syngenta. A list of other brand names under which paraquat is sold can be found here.
Paraquat is used in nearly 90 countries either to prepare the land for planting or for controlling weeds in more than 100 crops, including major food crops: corn, rice, soya, wheat, potatoes; major fruits: apples, oranges, bananas; beverages: coffee, tea, cocoa; and processed crops: cotton, oil palm, sugarcane, and rubber.
In this section you can find information about crops for which paraquat is an essential production tool and a selection of case studies illustrating the benefits from using paraquat in some very different cropping systems.
The crop reviews describe the crop, where it is grown and what it is used for; crop production methods and weed, insect pest and disease problems; and the key benefits from using paraquat. They are summarised here and more extensive articles can be found in the Knowledge Bank.
The case studies demonstrate why paraquat is an essential tool for use in sustainable agriculture, and one which many farmers around the world rely upon for their livelihoods and to support their families.
By providing the non-selective weed control essential in conservation tillage systems, paraquat is helping to mitigate climate change.
US farmers can now enrol in the Farmers Union Carbon Credit Program which means they will get paid for managing their cropland using conservation tillage systems like no-till and strip-till. Conservation tillage increases the amount of organic matter in the soil, and apart from being good agricultural practice, this sequesters large amounts of carbon dioxide.
Agricultural land has the potential to offset about 11% of US greenhouse gas emissions, equating to some 650 million tonnes of CO2 every year. Of this total, cropland could contribute 41% and half of this could be met by conservation tillage practices being adopted more widely. President of the Soil Science Society of America, Professor Rattan Lal (Ohio State University), has described this as a “win-win-win strategy, because it mitigates climate change, improves productivity and enhances ecosystems”.
Recently, the Soil Science Society of America published a series of articles about how conservation tillage can make a major contribution to carbon sequestration and how farmers can benefit from this by enrolling in carbon trading schemes.
Here’s how it works, how paraquat can help, and how we all benefit …
No-till on M&K Farms, Kansas
Over the years in many areas of the United States, certain weeds have become resistant to some herbicides used, most recently to glyphosate since Roundup Ready crops have been grown on an increasing massive scale.
Horseweed / marestail (Conyza canadensis) is native to the United States, but it has recently become much more problematic to control in Roundup Ready soybean production. Horseweed is well adapted to no-till crop production. It has developed resistance to several herbicides including glyphosate. Horseweed was the first broadleaved weed documented to develop resistance to glyphosate in the United States. Since this initial report, glyphosate resistance has been reported in several other states.
Dr L. Steckel is a row-crop weed specialist in Tennessee, USA. He has statewide extension responsibility as a weed specialist for all row crops. His research programme focuses upon the study of the biology and management of weeds that are troublesome to Tennessee row crop producers.
He already alerted about horseweed and palmer pigweed (Amaranthus palmeri) resistance in 2006 in an article published by Delta Farmpress.
Another weed can be added to the growing list of glyphosate-resistant weeds, according to an article from Western Farm Press published on August 28, 2006.
Author Harry Cline writes:
“Monsanto has confirmed that a Johnsongrass biotype has become resistant to glyphosate in Northeastern Argentina…. A preliminary assessment of the affected area identified the problem on 17,000 to 25,000 acres.”
The article also cites several approaches being used by manufacturers of glyphosate to address the increasing number of glyphosate-resistent weeds.  These approaches include a “recommendation for chemical control with herbicides other than glyphosate….”
Paraquat is one such herbicide that is playing an increasingly important role in Integrated Weed Management (IWM) programs associated with glyphosate-resistant weeds and in other situations where glyphosate has been intensively used for long periods of time.
Paraquat’s unique and rapid mode of action makes it an ideal tool in an ongoing resistance-prevention strategy. Paraquat acts in the presence of light to desiccate the green parts of all plants with which it comes into contact. For more information on paraquat’s unique mode of action, view The Science of Paraquat in the About Paraquat section of this website.
In the late 1960’s the US government, perhaps in an attempt to deter people from using marijuana, warned that much of the crop had been sprayed with paraquat and was, therefore, unsafe to smoke. However, independent bodies have studied paraquat in this use.
Jenny PronCzuk de Garbino1 stated: "no lung or other injury in marijuana users has ever been attributed to Paraquat contamination".
On this topic, D.P. Morgan states in a US Environmental Protection Agency publication that: "Smoking Paraquat-contaminated marijuana does not result in lung damage as the herbicide is pyrolyzed to dipyridyl (which does not present a toxic hazard) during smoking"2.
This is an unusual case and it is important to note that manufacturers of paraquat market the herbicide to kill green weeds and customers decide where to use it. However, these expert findings may be added to a long list of other crop safety studies, which support that paraquat does not represent a significant health risk to the public in normal use.
In their review report for paraquat the European Commission (EC) concluded “the review has established that the residues arising from the proposed uses, consequent on application consistent with [no-glossary]good agricultural practice, have no harmful effects on human or animal health” (EC, 2003)
Weeds. A single word that can strike fear into the hearts of farmers around the world. And it is no wonder. Effective weed control is essential for successful crop production - especially when using conservation tillage systems such as no-till or zero-till systems. These systems are designed to prevent soil erosion and reduce labor and fuel costs. However, in his article, entitled, “Weed Control Considerations for Conservation Tillage,” author Roger Veseth writes: “…lack of adequate weed control is one of the most frequently cited reasons for failure of conservation tillage systems.” While there are a number of integrated strategies that can be used to manage weed populations, in practice the sensible use of herbicides remain an essential tool for a sustainable, profitable production system.
Paraquat’s contact-only action allows farmers to control weeds without killing the weed root structure, making it an ideal herbicide for use in conservation and no-till systems. In fact, in addition to reducing soil erosion and improving soil moisture, field studies have shown that in no-till systems using paraquat:
Organic matter increases
Carbon dioxide emissions are reduced by allowing the soil to act as a better carbon sink
Microbial populations and surface microarthropods numbers increase