1 December 1995

Major step made for beet with new broad-leaf killer

A NEW herbicide for early post-emergence in sugar beet which controls a wider range of broad-leaved weeds than other materials will be available for next spring.

Du Ponts trisulfuron-methyl (Debut) is the first sulfonylurea herbicide approved for beet, and the first significant broad-leaved weed-killer to appear for 20 years.

"It represents a major step forward as it has a different mode of action to other beet herbicides, and increases the spectrum of weed control," said British Sugars Simon Fisher.

"It is particularly effective against cleavers, fools parsley, volunteer rape, mayweed, and charlock. This is combined with a sharp reduction in the amount of active ingredient applied, and improved crop safety."

Debut has contact and root uptake activity but only a short residual life. It will always be used in mixtures with existing post-emergence materials as their longer residual effect will be needed to remove late germinating weeds such as fat hen.

Trials conducted by Du Pont, British Sugar and Morley Research Centre show the addition of mineral oil to Debut/phenmedipham mixtures, with or without a residual partner, decreased crop biomass. This was clearly visible but not severe and had no effect on yield. But Mr Fisher thought it would be best to avoid using oil in mixtures applied to cotyledon beet, or stressed plants.

During the trials the new herbicide caused manganese deficiency-like symptoms to appear in the crop. This did not happen at every site and after every treatment, but could become obvious particularly on larger beet after the last treatment. The yellowing was cosmetic and had no lasting impact on the crop.

New beet herbicide offers wider spectrum of weed control, but could knock crop, says British Sugars Simon Fisher.