Weed Control in Young Pasture

New Pastures

Young pastures provide the opportunity to control thistles with clover friendly herbicides whilst they are still in the seedling stage. Once the thistles become more established, stronger chemicals are needed to control the thistles, and the option of using clover friendly herbicides is lost. Controlling thistles from the early stages is therefore essential:

Nodding Thistles

A young pasture should generally be sprayed for thistle control after approximately six weeks, depending on the growing conditions at the time. This is the ideal time to apply Tropotox, MCPB or Pulsar, whilst the thistles are still in the seedling stage. The clover should have reached the two leaf stage before application. These chemicals require warmer conditions, generally soil temperatures not below 10 degrees, and air temperatures 15 degrees. Application should ideally be followed by about 3 days of warmer weather, they are more important that the days preceding the application.

Baton has a recommendation for application at 1,5kgs/ha on white clover, or 1kg/ha on red clover, to be applied 3-5 days after the first full grazing, when most of the clover leaf area has been grazed off. This provides an option in colder conditions.

There are some weeds which are worth mentioning, as they are not controlled by some of the commonly used herbicides, and will require special attention:

Spurrey, Shepherd's Purse, Chickweed

These three weeds are commonly found in young pastures. They are inclined to grow prolifically, and choke out the new grass and clovers, slowing their growth considerably. These weeds are not controlled by Tropotox or MCPB. The addition of Preside plus Uptake Oil, which works particularly well on these three weeds, or Pulsar, helps to control these weeds, and to broaden the general spectrum of weed control.

I have seen many cases where these weeds have not been treated, and have become a problem. It is important to allow the newly planted pastures to get off to a clean start.

Speedwell

This weed is generally only a problem in the early stages of a new pasture. It can, like the abovementioned weeds, grow out ahead of the pasture, and choke off the new grass and clover. This may be controlled by Jaguar, but bear in mind there is a 42 day grazing withholding period. This weed does not tend to be a problem in more established pasture.

 

Storksbill

This weed is a problem in some areas, and if not controlled properly, it forms a thick mat over the pasture. This weed is not controlled by either Glyphosate or Granstar in the pre harvest spray out. The plant will appear to be drying out, but it will grow out again, and be present in the new pasture. An alternative would be to use Relay/Pasture Kleen with the Glyphosate, but a pre-planting interval of around six weeks to avoid damage to young clover would have to be taken into account. If the weed is present in new pasture, Pulsar would be a good choice.
Baton is effective on younger storksbill, see the information under Nodding Thistles regarding use of this chemical on young pasture.

Nettles

This weed can be a major problem, virtually taking over the land and choking the grass and clover out, seriously hindering their growth and development. It will outgrow the pasture, so early control is essential. At that early stage, Baton or Pulsar would be options, see notes under Nodding Thistles regarding the application on young pasture.

 

Docks

If you have a bad dock problem, make sure you deal with them in the pre-planting spray out. Harmony cannot be applied in the first year, and there will be no way of controlling the docks for that period of time. Glyphosate will not effectively control this weed on its own, a good option would be to add Harmony to the Glyphosate mix.

Pre-Planting Spray Out

For those planning to direct drill new pastures, spraying out before drilling will play an important role in weed control in the new pasture. The established thistles will have to be killed off, as well as any problem weeds. Herbicide choice is important in this situation, remember Glyphosate is not a one off herbicide that kills all, the addition of a broadleaf herbicide may be necessary. Some examples of weeds not effectively controlled by Glyphosate on its own are: thistles (particularly established thistles), shepherds purse, storksbill, spurrey, docks, yarrow, dandelion, ragwort. If there is a lot of couch in the land, remember spring control is not as effective as autumn control. In many cases people have had unrealistic expectations regarding couch control in spring, and end up with new pastures with a lot of couch growing in it, a very undesirable situation. If you do have a lot of couch in the land, you may need to rethink your cropping program in that land.


It is important to always read the label on any chemical used, to follow the instructions and take note of and comply with the information on the label.

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