Q. Paraquat is a non-selective herbicide, have transgenic crop plants been developed that show in-built resistance to paraquat?
A. No. There are a number of reasons why herbicide tolerance to paraquat has not been commercialized. One key reason is that the mode of action of paraquat is so fast that it is technically difficult to achieve effective resistance. Also, where glyphosate resistant crops are introduced there is always the risk that herbicide-resistant plants emerge as weeds in successive crops and reduce the effectiveness of weed control. Therefore, the major manufacturer of paraquat, Syngenta, made the decision not to introduce transgenic paraquat crops to ensures that paraquat remains a highly effective tool (pre-plant, burndown herbicide) to manage glyphosate-resistant weeds.