Control of perennial weeds – such as docks, thistles and buttercups – is easier and more cost-effective in new-sown leys than spraying mature, fully established weeds a year later. So says Corteva Agriscience’s weed biology specialists Nicola Perry.
“Producers can gain a higher rate of control of broad-leaved weed seedlings in new-sown leys, compared to treating them the following year, when they have developed a deep root system,” she says.
Grass reseed trials, carried out by Teagasc in Ireland some years ago, showed that plots treated soon after reseeding were completely clean of docks when assessed four years later, compared to plots where a higher dose product had been used the following year. These still had docks growing in them.”
Oliver Seeds’ BASIS-registered seed adviser John Harris says that where producers are spending up to £500 per ha, or more, to reseed their leys, a zero-tolerance approach should be taken towards perennial and annual weeds, to ensure their investment realises the required productivity gains.
“There are clear differences in leys that receive early weed control and those that do not, with weed populations in the latter becoming bigger and stronger the following year, sapping nutrients and moisture which should be going to the grasses,” he says.
“Producers must keep a careful and regular eye on their new reseeds at this time of year to see if they need treating,” he adds. “Herbicides should be sprayed onto small and actively growing weeds, for example when a dock leaf is the size of a £2 coin.
“Attention to detail at the time of sowing – from cultivations through to nutrient application and correct seed choice – will ensure that the grass jumps out of the ground, quickly taking over any bare patches left by the dead weeds.”
Leystar and Envy, both from Corteva Agriscience, are effective options for use on new-sown leys, defined as grass that is up to one year old. They can be applied once the newly emerged grass has reached the three-leaf stage.
“Leystar and Envy will not harm very young grass, but they are not safe to clover. If required, clover can be stitched in three months after application,” adds Dr Perry.