Applying a herbicide to a new grass ley is the most cost-effective spray you will use on that field, according to Teagasc

It stresses that the control of docks, thistles and chickweed, etc., is much easier when these weeds are seedlings.

Product choice is decided by the presence or absence of clover in the new ley. Clover-safe products include Legumex DB, Undersown DB Plus, Clovex, Triad and Underclear. Starane 2, Binder, Hurler and Reaper are not clover safe.

However, Teagasc warns that farmers should remember straight versions of CMPP (Duplosan, Optica, etc.) and MCPA are no longer registered for use on grass.

Yes (in most cases) as there are up to 100,000 dock seeds per acre ready to germinate in fields.
Yes as you will kill all weeds more easily when they are seedlings.
Yes as you will maximise your investment.

Teagasc research shows that reseed sprays provide very good control of docks for four years after application, whereas mature sprays provide control for just one year

have an even, vigorously growing sward;
apply the herbicide onto small, actively growing weeds (e.g., dock leaf = size of €2 coin);
spray six to eight weeks after reseeding when there are three leaves on the grass and one true leaf on the clover;
avoid spraying in very dry or cold conditions (talk to your adviser/merchant if this is the case);
keep water rates high: 220-350L/ha (20-30 gallons per acre); and,
remember to keep the prescribed crosscompliance records and follow the product label.