Weed Control In Newly Sown Leys

Establishing a new ley is an expensive business so it is important to ensure it establishes evenly and rapidly to be as productive as possible.

The key to good even establishment is of course ensuring a good seedbed and adequate pH and nutrient availability, but once the grass is sown, keeping weeds out becomes equally important. Early competition from vigorous weeds such as chickweed and mayweed can rapidly reduce the growth of grass and leave new leys ‘gappy’ and unproductive. An uneven grass ley can take a considerable time to become fully productive. This is particularly true if the ley also contains clover.

Many grassland herbicide products dictate that grass should be ’established’, i.e. over a year old at the time of treatment. In addition, many cannot be used in clover leys. The number of available herbicides for newly sown leys is limited, particularly where clover features in the sward.


Newly sown grass leys, (ie. those under one year old) fall into two distinct types:

• Pure grass sward
Grass and clover mixture

One of the best options for early weed control in any new ley is Triad. It is safe on pure grass leys and also, importantly, on grass and clover mixes (both red and white clover). Triad can also be used on spring barley undersown with grass.

Triad will control chickweed and is currently the only clover safe product available in the market that will control large chickweed in young leys. Other species where good control may be expected include:

Scented Mayweed
Shepherd’s Purse
Seedling Broad leaved Dock

Triad provides control of seedling broad-leaved docks up to a maximum of 4 true leaves. However, it should be noted that adult docks or those regenerating from root pieces may not be controlled.

When to apply:
Triad is best applied when weeds are young and actively growing, during a period of warm days and warm nights. The product should be applied from the three true leaf stage of the grass and, if present, when clover is at the three trifoliate leaf stage or later.

Where grass leys have been established in the autumn and the weed burden is high, Triad in combination with a Phenoxy partner may be the ideal solution.

This is for several reasons:
• SU chemistry is inherently slow in activity, and a Phenoxy partner will speed up the initial rate of kill
• The Phenoxy partner will broaden the spectrum of activity
• It will act as an anti-resistance strategy to protect the SU group of active ingredients

We would recommend using a tank mix with Headland Spruce. This mix is clover safe.

Headland Spruce will improve control of annual species such as Sow-thistle, Small nettle, Charlock, Fat-hen as well as improving activity on perennial weeds such as Creeping buttercup, Creeping thistle and Plantain.

To make life easy, and where weeds are still quite small, making a tube of Triad treat 4ha, and a 2.5l/ha dose of Spruce (10 litres) makes the two packs match.

Triad contains 50% w/w Tribenuron, Headland Spruce contains 400 g/l 2,4-DB

Written by Simon Pope – Crop Protection Manager
For more information dairy@wynnstay.co.uk

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