Corteva Agriscience said SQPs and farmers should be planning to spray dock infestations in silage leys in April, three to four weeks before the mower goes in.

Dave Gurney, field technical manager for grassland crop protection products at Corteva Agriscience, said: “I am sure most grassland farmers have a target date for first cut silage, but doubt whether they have a similar date in mind for an early season dock spray.

“Destroying docks this side of harvesting will maximise the yield and feed quality of the silage. If a spray contractor is used, a date should be booked in now.”

A 10% dock infestation can reduce grass yield by a corresponding 10%. They also have only 60-65% of the feed value of grass and can restrict silage fermentation, leading to lower dry matter intakes.

Dock seeds can also survive in silage and pass out through cattle, infesting fields that previously had no problem or re-infesting fields that have already been treated.

The ideal time to spray docks with an effective translocated product such as Doxstar Pro, is when the plants are young and actively growing and the size of dinner-plates.

Mr Gurney said: “Spraying three weeks before cutting allows the sprays to reach down to the roots to kill the plant and for the leaves to decay. Early season sprays also mean docks are all at the same stage of growth, making it easier to treat them all.”