28 November 1997

Herbicide trials 99% success

NEW pre-emergence herbicide, JV485 (isopropazol) from Monsanto and Bayer, is unaffected by any of the known resistance mechanisms found in the UK, according to IACR Rothamsted.

Outdoor pot tests using the herbicide at the recommended rate gave 99% control of resistant plants from six UK sites, reports Stephen Moss.

A similar level of control was achieved in a Rothamsted field heavily infested with blackgrass highly resistant to fenoxaprop.

The field result is particularly encouraging, suggests Dr Moss. "There were more than 1000 blackgrass plants a square metre and the crop was fairly thin because of rabbit damage.

"That meant there was a lot of potential for weed tillering and regrowth," he says.

So far in the US, where such protox-inhibiting herbicides have been used mainly on non-cereal crops for 30 years, no weeds appear to have developed resistance to them, says the USDAs Frank Dayan. &#42