17 November 1995

World launch for anti-resistance plan

A NEW scheme to help growers fight herbicide resistance in weeds is set for a worldwide launch.

Due to be outlined in Brighton next week, it aims to help growers choose the right herbicide to manage and delay resistance.

"Ringing the changes" when choosing products is one of the key management steps growers can take to counter the threat of resistance to previously effective weed-killers, says session organiser Dr John Caseley.

Along with other measures, such as rotating crops and adopting as much cultural control as possible, using materials with different chemistry and modes of action is vital, he explains. This applies both to sequences and mixtures.

"The trouble is that unless growers know what the chemistry and modes of action are they can be working in the dark. Unless you know that, say, sethoxydim and fenoxaprop have the same target sites in the plant you might think you are already rotating your herbicides," says Dr Caseley.

Makers selling active ingredients under different product names add to the confusion, he suggests. At Brighton, Zenecas Dr Alan Jutsum and Dr James Graham will highlight moves in Australia. A labelling scheme drawn up there has been made compulsory.

All herbicide labels must carry large, lettered symbols identifying the contents mode of action. Dr Jutsum describes it as an "excellent initiative" and notes there are proposals to develop similar systems in other countries.

But he sees it as "critical" that a single, uniform lettering scheme is introduced globally. The UKs Herbicide Resistance Action Committee, which consists of representatives from 13 big manufacturers, is working with bodies such as the Weed Science Society of America to achieve this.

Already HRAC has drawn up a proposed list of 16 types of herbicide classified according to their modes of action and tagged A to P. The idea is to avoid repeated use of chemicals from cans with the same letter.

The latest move is largely manufacturer driven, says Dr Caseley. "The industry realises it has a problem and stands to lose a lot if resistance really takes off."

But can resistance be contained? Dr Jutsum maintains that counter strategies could have managed or prevented the problem in almost all cases so far. No commercial herbicide has yet been lost due to weed resistance, he adds. &#42

&#8226 Identifies mode of action.

&#8226 Helps avoid unwitting repeat treatment.

&#8226 Letter-based.

&#8226 Worldwide scheme is aim.

The battle between weeds and chemicals is hotting up.