Producers should be planning to spray dock infestations in silage leys in April, three to four weeks before the mower goes in.
So says Corteva Agriscience’s Dave Gurney, who adds that removing docks this side of harvesting will maximise the yield and feed quality of the silage.
“Most producers have a target date for first-cut silage, but I doubt that they have a similar date in mind for an early season dock spray,” says Mr Gurney. “But 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%. Docks also have between 60% and 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 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.
Spraying three weeks before cutting allows the spray 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. Controlling docks at the start of the season also avoids the need to top them.
“Using a contractor to top grass and any weed infestations costs £32/ha, whereas spraying costs, excluding the product, just £12.50/ha,” says Mr Gurney.
“Topping is more expensive because it is carried out at a slower speed, uses more fuel, and works on a narrower working width than spraying.
“Even with the cost of the herbicide added in, spraying once early in the season will always be the best value option and will reduce the number of tractor passes and consequential soil compaction.”