Grassland Update – October 2020

Weeds in autumn re-seeds

The best start for an autumn re-seed is to have sprayed off the old sward with glyphosate to establish a sward free of perennial weeds. If the old sward had perennial weeds and was not sprayed off, then there could be dock, thistles and nettles re-growing from root and rhizome fragments. These are difficult to control in a young sward.

Weeds that have established from seed can be controlled – it is well worthwhile controlling docks established from seed when they are still small.

If the sward has been sown without clover then if the weather is mild, fluroxypyr is an option. This will control seedling docks and small chickweed. Another option is 2,4-D + MCPA which has a recommendation for autumn use on new grass, it has a broader weed spectrum, but is weaker on chickweed. Do not use if overnight frost is forecast. In cooler conditions, the fluroxypyr + florasulam is likely to be most effective.

Where clover is present, tribenuron + 2,4-DB can be used. The grass should have three leaves and/or be tillering, clover should ideally have reached the three trifoliate leaf stage.  A range of annual weeds are controlled as well as dock seedlings that have grown from seed. Another product to consider if clover is present is 2,4-DB + MCPA which also controls a range of annual weeds, but not chickweed. Grass should have four leaves and have begun to tiller, clover should have one trifoliate leaf on the majority of plants. Do not use if frost is forecast.