Weeds in new leys

Thursday 17.06.2021 , events , news

The best start for new leys

Paying attention to detail when establishing new leys can pay dividends, giving the new sward the best start possible. Creating a firm seedbed with adequate soil pH and fertility is essential for establishment, but equally important is management of the new reseed after sowing to encourage tillering and minimise weeds.

Post-emergence spraying is therefore a vital part of any reseeding programme but often overlooked. Tackling weeds is easier and cheaper when they are small and offers the new sward chance to establish with less competition for light, water and nutrients.

Are all weeds a problem?

Annual weeds such as fumitory, fat hen and deadnettle are usually found in small numbers so don’t cause problems when establishing a new sward. They only live for a year and can normally be controlled through grazing. However if they appear in high numbers it may be necessary to spray.

Perennial weeds, such as chickweed, dock and thistle, are those more likely to cause an issue with reseeds. Even at low populations they pose a significant threat to productivity. A 10% infestation has been shown to cause a 10% loss of yield. With chickweed particularly aggressive and the root of an established dock plant able to reach more than one metre deep, it is much better to eliminate them while small.

Timing is everything

Timing is critical to the efficiency of any treatment. Treat too soon and the weed seed may not have germinated, but left too late, when the roots have had time to develop, and the spray may be less effective. Always follow the manufacturer’s recommendations, using the correct dosage and water rate as detailed on the product label.

Choice of product

It is important to only choose herbicides approved for use on new leys so check the product information carefully. Likewise, if the sward contains clover, choose a clover-safe spray or stitch in clover separately three months after application. Your merchant or a qualified advisor can advise on product choice.

How to spray successfully

  • Only spray when conditions are good. Avoid spraying if rain is forecast or if it is very dry, cold or windy
  • If your sward includes clover, use a clover-safe product. Emergency use has been granted for Clovermax (valid until 11 September 2021)
  • Apply herbicide to small, actively growing weeds. For example, when dock leaves are around the size of a €2 coin
  • Check weeds are at the correct growth stage and when there are three leaves on the grass and one true leaf on the clover. This will be approximately 5-6 weeks after re-seeding
  • Always read the product label, follow the correct application and water rates and any other prescriptions detailed by the manufacturer
  • Remember to keep cross-compliance records
  • Contact your merchant/advisor if you have any queries or need advice.


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