Don't treat grassland weeds too early

UK - March 12, 2008

That's the advice from Duncan Connabeer, Dow Grassland Agronomist.  "It looks as though we're following a similar weather pattern to last year with a relatively mild winter," he explains.  "We know this encourages people to think about applying weed control herbicides earlier; farmers and agronomists are understandably keen to get on top of grassland weeds, but we've found many people are still applying it too soon.

"The docks here are looking very fit, which makes me nervous!" says Cornwall Farmers Agronomist Nora Lehane.  "In silage the docks can get overshadowed by the grass, which makes them difficult to reach until after first cut, but if we go too early with a herbicide the chances are we won't get good control.

"To get the maximum benefit from applying a herbicide such as Forefront [aminopyralid] which we used very successfully last year, the most important point is that the weeds are in active growth," she explains.  "This means the active ingredient is translocated throughout the root system, and will kill the weed throughout.

"The mild winter has meant that weeds have come forward, but the recent cold snap means they will be affected by the frost and will not be receptive to the active chemical."    

Mr Connabeer strongly advocates holding back the herbicide application until the optimum time.  "Weeds might look ready for treatment," he says, "but it's often still too early.  Docks may have emerged and actually appear to be at the right growth stage to treat, but the recent cold will have stressed the plants and turned the weeds red, so they won't be growing in the best of health.  You don't get the best results from treating stressed plants.   In the south and south-west of the UK April is the peak time for treatment before first-cut, so you should really only consider spraying from the middle to the end of March at the earliest in those areas.  And across other regions the optimum timing tends to be during May and June, depending on the growing conditions."