26 November 1999

Ploughing-resistance link

PLOUGHING will delay the onset of target-site resistance in blackgrass by up to 30 years. By contrast continued use of tined cultivation could lead to resistance developing in just seven years.

Those are key conclusions from a new model of resistance patterns developed by IACR Rothamsted. "The delay in resistance is roughly proportional to the amount of ploughing included in the rotation," researcher Graham Cavan says.

"There is a very big effect on the development of resistance when we introduce herbicides with different modes of action. For really long-term control we need three modes of action."

With wild oats, ploughing again delays the development of resistance. "But the effect is not nearly as big as with blackgrass," he says. However, resistance develops more slowly in wild oat populations, and if herbicides are rotated resistance could be delayed for over 100 years, he says. &#42

ANTI-RESISTANCEADVICE

&#8226 Ploughing is beneficial.

&#8226 Use three alternative herbicide modes of action.

&#8226 95% control target – all applications.

&#8226 Collect seed and screen for resistance.