Syngenta has launched a new contact herbicide, Retro, as a direct replacement for the paraquat-containing PDQ, which will be withdrawn from use in the UK on 11 July 2008.

Retro, which contains 200g/litre of diquat, had full approval for use in potatoes, sugar beet and vegetable crops, including peas and beans, and could be used in the same way, with the same mixtures and at the same rates as growers used for PDQ, says the firm’s Simon Parker.

“Growers now have a simple direct replacement for PDQ. It will be recommended for use as an early post-emergence treatment, in mixture with partner residual herbicides.”

Research at the Syngenta Jealott’s Hill Research Station had shown the new herbicide’s control of key potato broad-leaved weeds, including speedwells, cleavers, chickweed, groundsel and fathen, matched PDQ for speed and efficacy, he claimed.

Where Retro is used in combination with a residual herbicide, such as Defy, there is no need for an additional adjuvant, but when used alone to clean up spring seed-beds, adding a non-ionic surfactant adjuvant will enhance activity.

The new product would cost about 15% more than PDQ, Mr Parker said. “But it is still markedly cheaper than alternative contact herbicides, such as carfentrazone or glufosinate.”

Growers have until to 11 July 2008 to use up any remaining stocks of PDQ.