Winter Thistle Control

Thistles As we move into winter, the opportunity arises to deal with established thistles in pastures whilst limiting the clover damage as much as possible. This opportunity should not be missed.

If you have young pasture, the opportunity to use MCPB/Tropotox may have passed, as they require soil temperatures of around 10 degrees, and an average daily temperature of around 15 degrees. An option is to apply 1 – 1.5kgs/ha of Baton 3 – 7 days after the first full grazing. It is important to graze the paddock 3 – 7 days prior to spraying, as this both exposes the weeds and removes much of the clover leaf, thus reducing herbicide uptake by the clover and minimizing damage. If red clover has also been sown, use a maximum of 1 kg/ha Baton to minimize damage. Higher rates will cause red clover mortalities. If you do not apply Baton after the first full grazing, and wait for a subsequent grazing, the level of weed control may be reduced as the weeds will be larger.

In established pasture situations where mature thistles are found, now is an opportune time to control them. Mature thistles will not be controlled by more clover friendly herbicides such as MCPB or Tropotox, so stronger herbicides will need to be used, and therefore there will be some clover damage. However, the damage can be limited by applying the chemical when the clover growth has slowed right down due to the colder conditions. Although it is tempting to wait until conditions are at their coldest in mid-winter in order to limit the clover damage as much as possible, by that time the thistle growth will also have slowed right down which may limit the uptake and therefore the efficacy of the chemical. In some situations Agritone/MCPA or Pasture Kleen/Relay on their own may be sufficient, but where there are well established crowns on the thistles, the addition of Vivendi/Versatill may be necessary. The rate of application would depend on the severity of the thistles. I can not make a blanket recommendation, so if you would like advice on the choice of chemical, and rates of application, please contact me for an on farm visit in order to make recommendations.

Steve Lawson is the ATS Field Rep. Please contact him for any further information or assistance, or if you would like an on farm visit. He may be contacted by mobile:
027 24 55 661, or via ATS during working hours. Or e-mail steve@ats.co.nz