Did you miss the news about paraquat?

More modes of action needed to support glyphosate tolerant crops

Resistant weeds (C. canadensis pictured):  The Achilles heel of glyphosate tolerant crops The introduction of glyphosate tolerant (GT) crops has been the one of the most significant technological changes in agriculture. Farmers around the world are reaping the benefits of a simplified weed control system, saving costs, time and labor and increasing operational flexibility. However, relying heavily on a single herbicide mode of action to control weeds encourages the evolution of resistant populations. Unfortunately, farmers tend to only change weed control strategies once resistance has been recognized in their fields. This generally results in substantial cost increases to attack established resistant populations. In the long-term, preventing the development of glyphosate resistant weeds and avoiding the need for expensive control strategies will generate additional substantial savings. Weed control systems integrating paraquat retain the benefits of glyphosate while markedly reducing the risk of resistant weeds appearing. Read more ...

Paraquat gives flexible weed control in potatoes

Potatoes saved from weeds by paraquat Paraquat is a very useful herbicide for potatoes because it can be used to burndown weeds from before planting right up to the point at which the potato sprouts start to emerge from the soil. As potatoes may take up to four weeks to emerge, significant weed growth may have occurred after planting. Weeds can quickly overrun potato crops if they are allowed to grow unchecked before the crop leaf canopy closes. They compete with potato plants for light, water and nutrients, so if they are not controlled weeds reduce yield and quality. In addition, large weeds entangle the crop and interfere with harvesting. Weeds may also encourage pests and diseases. Filling the crop canopy, they restrict air flow, increasing humidity under which fungal diseases, especially potato blight (Phytophthora infestans) thrive. Blight can devastate potato crops so intensive use of fungicides is needed to achieve control. Paraquat is inactivated and immobilised immediately on contact with the soil, so cannot affect the seed potatoes, or later, the developing crop of tubers. Read more ...

Paraquat wipes out superweeds

Paraquat being applied by a weed wiper Paraquat has been found to be an effective ‘fire fighting’ treatment for large glyphosate resistant Palmer amaranth, sometimes called a ‘superweed’. Since 2005, Palmer amaranth (Amaranthus palmeri) has become an increasing problem for farmers in Georgia and neighboring states. It has become common for gangs of laborers to be used to remove weeds with hoes and machetes often at a cost of over $100 per acre ($250/ha). Researchers at the University of Georgia, USA, have found that applying paraquat through weed wipers and similar implements can very effectively kill Palmer amaranth plants up to 5ft (1.50 m) tall.  Weed wipers have been developed to apply glyphosate to tall weeds standing above crop canopies. University of Georgia researchers tested a number of alternative herbicides through weed wipers of various kinds. They found that paraquat proved to give a surprising and exceptionally high level of control, and was clearly the best option. Treatment costs around $4 per acre ($10/ha) for the herbicide. Read more ...

Green light for China’s red soils

Red soil no-tilled for 10 years (right) has much better structure and fertility through more organic matter No-till crop production using paraquat for weed control is enabling the successful cultivation of one of China’s last available soil resources for food production. At present, nearly 30 million hectares of red soils have been cultivated, but they are highly weathered, inherently infertile and very susceptible to erosion. No-till can help by stabilizing the soil to resist erosion and by conserving water. The higher levels of organic matter in no-till soils are also crucial to raising soil fertility. Over the past few years research has demonstrated how the successful cultivation of red soils on steep slopes starts with weed control. Trial plots were established in peach orchards and tea plantations to compare traditional farming techniques of hand-weeding and tillage with the use of paraquat and no tillage. The benefits of using paraquat soon became obvious. For example, water run-off


The occurrence of surplus liquid (like rain) which originates up-slope and is collected beyond the ability of the soil to absorb it. The surplus liquid then flows away over the surface to reach the nearest surface water (pond, lake, river).

Authoritative On-line References and Resources

US Geological Survey's Water Science School
from land with a slope of 25 degrees and weeded by hand averaged 427 m3 per hectare per year, whereas when using paraquat it was only 224 m3. Loss of topsoil using traditional farming averaged 2.3 tonnes per hectare compared to only 1.3 tonnes per hectare with paraquat and no-till.
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