16 February 1996

Waging war on beet weeds

SUGAR beet weed control is approaching the "light at the end of the tunnel," according to Simon Hopkinson of British Sugar. "But we are not in daylight yet."

Visitors to the ADAS Arable Centre/DowElanco conference in Peterborough were given a curtain raiser on one of the latest approaches. The idea is to control weeds with two passes of a contact action, post-emergence herbicide, he suggested.

Three years of trials show the most effective time for the first spray is between two and three leaves of the crop. The second spray timing seems optimum when the crop has four to six leaves.

A farmer trial in 1995 compared a two spray programme on a 4ha (10 acre) block with the remaining 16ha (40 acre) of the field receiving a programme of a pre-emergence, three-post emergence and a clopyralid (Shield) spray. Results were "very good", matching those of the more conventional programme.

By comparison some 1995 trials receiving a "blueprint" approach where the choice of spray was made without field inspection "did not work well".

The two contact herbicide system is seen to suit lower weed pressure non-organic soils. However, some weeds may cause a problem – notably knotgrass. "But if the weed is suppressed by the herbicide it may be hit by mildew later on," noted Mr Hopkinson.