OILSEED RAPE growers with crops still to desiccate this season must take care to avoid chemical drift to nearby hedges, one conservation charity has warned.

While many growers have started harvest, those with desiccation still to do should be aware that glyphosate readily volatilises in warm conditions and can move several metres in convection currents, the Countryside Restoration Trust said.

This can cause permanent damage to species such as hawthorn and blackthorn, while others like dogwood and hazel appear less affected, said the Trust’s John Terry.

The problem is worse where more concentrated mixes – i.e. 100 litres/ha water – are used, he said. Such mixes are often used in pre-harvest applications in cereals, he noted.

In order to cut the risk of spray drift, growers should reduce boom height and select a low drift nozzle, added Syngenta’s application specialist, Tom Robinson.

Trials at Silsoe Research Institute have found that the best results are achieved with the boom 40-50cm above the rape crop, but increasing this to 70cm doubles the drift risk, he said.

Both experts agree that boom suspension is also important in maintaining consistent nozzle height and so reducing drift risk.