7 March 1997

Beware Debut cuts

CUTTING rates of new beet herbicide Debut (trisulfuron-methyl) could jeopardise weed control when cold weather slows weed growth.

That was one of several lessons learned last year and relayed to growers at ADASs Peterborough root conference by Lincs-based agronomist John Youles. He questioned the products role as a spray for the T1 timing.

The chemical, which was launched last season, had been impressive on target weeds like fools parsley and cleavers. But it was probably weaker than maker Du Pont expected on polygonums particularly knotgrass, he said. Unlike sulfonylureas used on cereals, the beet version needed more warmth to work well, he explained.

Choosing an appropriate mix partner, such as ethofumesate, in sufficient strength to deal with early knotgrass was important.

With only five to seven days soil activity from Debut, there could also be problems with late germinating weeds, especially fat hen in June, Mr Youles noted. Debut lets growers control larger weeds than in the past, but is not the complete answer, he added.

On the strength of field experience Mr Youles believed the chemical was more suited to T2 and T3 timings. More work was also needed to assess its value in controlling volunteer potatoes.

lDu Pont spokesman John Austin maintains a two-spray sequence at T1/T2 is still the preferred option for Debut. "But a T2/T3 programme also fits well after conventional T1 treatments," he says.

Contrary to the ADAS view, Morley Research Centre work indi-cates that knotgrass control was better than anticipated, Mr Austin adds. &#42


DEBUT ON BEET


&#8226 Valuable extra tool.

&#8226 Beware rate cutting.

&#8226 Needs appropriate partner.

&#8226 T1 timing debatable.