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Paraquat’s famous fast speed of action has been captured by a time-lapse video produced by Ohio State University, USA. No herbicide acts faster than paraquat and across such a broad spectrum of weed species too. Fast action gives farmers important benefits including opportunities for higher yields and better prices through earlier planting; rainfastness within 15-30 minutes; and ease of seeing where weeds have been treated after a break in spraying operations.
Ohio State University chose giant ragweed (Ambrosia trifida) as the target for paraquat in this video¹. Despite being one of the tougher weeds for paraquat to control, the ragweed in the video is desiccated over the course of a day with effects clearly visible after only a few hours.
You can watch the video here
Mixing paraquat with 2,4-D or a photosynthesis inhibitor herbicide such as metribuzin will give the best control of giant ragweed.
A similar video showing the time course of glyphosate effects on common ragweed (Ambrosia artemisiifolia) is also available. Glyphosate takes around one week to desiccate the weed. You can watch the video here
Why ragweeds?
Ragweeds are native to North America and classed as summer annual broadleaved weeds. They are amongst the earliest weeds to emerge in fields to be prepared for spring crops.