Information for Farmers and Ranchers

Following is information for ranchers and farmers about the use of aminopyralid herbicides.

What is aminopyralid?

Aminopyralid is the active ingredient in several herbicides registered for agricultural uses, including Milestone®, ForeFront® R&P, Chaparral, GrazonNext and CleanWave herbicides. Since coming onto the market in 2006, aminopyralid-based products have proved extremely effective in controlling troublesome and poisonous rangeland and pasture weeds such as thistles ragweeds, knapweeds and star thistle at rates significantly lower than other commonly used herbicides.

Herbicides containing aminopyralid provide excellent control of noxious and invasive weeds and some sensitive woody plants at rates significantly lower than commonly used herbicides. The active ingredient has an excellent environmental profile and is effective for controlling and eliminating many rangeland and pasture weeds including thistles, ragweeds, knapweeds and star thistle.

When rangeland and pasture is sprayed with aminopyralid, it kills target weeds but does not affect grasses. However, when this grass is eaten by animals, either out in the field or as hay, a small amount of aminopyralid may pass through in the manure and urine.

How can I safely and effectively use aminopyralid?

Follow all label directions, use precautions and restrictions and best management practices.

Consult your Dow AgroSciences sales representative, dealer or distributor for specific crop advice.

Refer to the  Range & Pasture aminopyralid stewardship guidelines.

Manure and hay management

Manure that has been generated by animals grazing on grassland or hay treated with aminopyralid may contain residues of aminopyralid. After ingestion, aminopyralid takes three days to completely pass through an animal. Manure produced during those three days can only be used to fertilize rangeland, pasture or fields where wheat is or will be grown. There is no restriction on the use of manure produced by animals that have grazed for at least three days on untreated pasture or hay.

Growers of sensitive crops need to avoid the use of manure that may contain aminopyralid residues. Similarly, farmers who use aminopyralid herbicides need to ensure they do not inadvertently supply affected manure or treated hay without informing recipients of the hay or manure about use precautions and restrictions.  Manure from animals that have eaten forage treated with aminopyralid-containing herbicides must not be applied as a fertilizer where sensitive crops are or will soon be grown, such as potatoes and beans, or be used on gardens or for mulch or compost.

Avoid neighboring crops/plants

Avoid damage by drift onto susceptible crops, nontarget plants or waterways. Do not apply directly to, or allow spray drift to come into contact with agricultural or horticultural crops, amenity plantings, gardens, ponds, lakes or watercourses.

What should I do if I treated grassland with aminopyralid?

Where land was grazed and the manure generated from grazing remained on or was returned to the grassland, then there are no issues.

Where hay was fed and the resulting manure was returned to rangeland, permanent pastures or wheat fields, there are no issues.

Where hay or silage, which you think may contain aminopyralid residues is sold, you need to inform buyers about this and the restrictions for the use of any subsequent manure produced from animals eating treated hay. Similarly, tell your customers if you sell manure or slurry that could contain aminopyralid.

What should I do if I grow any of the sensitive crops?

Farmers intending to plant crops other than wheat should make sure aminopyralid has not been used on the land in the previous year.

Where manure is to be used as a fertilizer with any of these crops, it is important to establish that it does not come from livestock fed on forage from aminopyralid-treated rangeland or pasture.

How does aminopyralid degrade?

Aminopyralid is degraded in soil when it comes into contact with soil microbes, but it degrades very slowly in manure or compost. Do not rotate any field treated with herbicides that contain aminopyralid within one year following treatment, and not until an adequately sensitive field bioassay shows the amount of herbicide present in the soil will not adversely affect the rotational crop.

What Can I Do?

  1. Read and follow label directions.
  2. Contact your Dow AgroSciences sales representative if you have any questions.
  3. Only spread manure and slurry from treated grass onto pasture or land intended for rangeland, permanent pastures, wheat or fields with grass grown for seed.
  4. Inform customers who buy hay or silage made from treated grass about the restrictions for any manure produced from animals that eat it.
  5. 5. Inform customers who buy manure that could contain aminopyralid so that they do not apply it to ground where sensitive crops are to be grown.

Contact Dow AgroSciences

To contact Dow AgroSciences please call your sales representative, or the Customer Information Group at 1-800-992-5994 and use Option No. 4; or e-mail