Cold weather in November and December, followed by a mild January have caused the deadly weed ragwort to start to grow early.
And landowners are being urged to start spraying now to remove the weed from their pastures.
A spokesman for herbicide manufacturer Micron said: “Having survived one of the coldest Decembers on record essentially unscathed ragwort and spear thistle in particular are already moving, especially in the southern counties and require herbicide application targeted at the leaf rosettes now.
“Once established and allowed to grow, spread and multiply during late spring and early summer these weeds become difficult if not impossible to shift.
“However, if hit early in the year while still in a sluggish state, they are easily and quickly dispatched.”
