Dirty sprayers left out in the rain may result in pesticides reaching water, a leading pesticide application researcher has claimed.

Research at Harper Adams University College by Simon Cooper has shown that spraying for just one hour with a fine spray resulted in 10g of pesticide on the outside of the sprayer.

"If this was to get into water it would be enough to put 100bn litres of water above the EU drinking water standard," he warned.

That could be easily avoided with a little bit of common sense, Steve Higginbotham, environmental stewardship manager at Bayer CropScience said.

He recommended growers followed three rules:

• Ensure the right spray quality is used - wherever practical it should be a medium coarse spray
• Wash down sprayer exteriors at the end of each day before leaving the field
• Park the sprayer under cover when it is not in use