Frequently Asked Questions

In response to inquiries about the proper use of aminopyralid, the following are some frequently asked questions and answers to help you find additional information.



Q: Who registers herbicides for use in the United States?

Review and registration of all new pesticides is the responsibility of the U.S. Environmental Protection Agency (EPA). Additional registration, review and acceptance is required by each state.

Stringent requirements must be met to demonstrate that use of the pesticide does not pose unreasonable risk to the environment, farm and domestic animals or humans. It also must deliver a level of performance that equates to the claims made on its label. Pesticides not meeting these stringent standards do not gain registration.

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Q: If these products can cause problems, why are they allowed?

For farmers, ranchers and vegetation managers, aminopyralid herbicides deliver highly effective weed control. Aminopyralid works especially well on difficult-to-control weeds, such as thistles and docks, as well as weeds that are potentially dangerous to livestock, such as ragwort. Aminopyralid herbicides can deliver a level of control that frequently removes the need for a follow-up treatment, so less herbicide is used overall.

If herbicide users follow the EPA accepted label, there should be no reason for residues to be found in manure in your garden.

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Q: How can I keep herbicide residues out of my garden??

Be aware of the potential of herbicide residues to be in manure or compost. Ask the source of the manure or compost if they know whether the manure came from animals that may have grazed on fields or hay containing aminopyralid. If they are not sure, you can use a bioassay test before adding the manure or compost to your garden to determine that it will not damage sensitive garden plants.

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Q: If my garden plants have been damaged, can I still eat the produce?

There are many potential causes for the damage you may be seeing to your garden plants. It is important to know what is causing the effects you are experiencing before determining whether you can eat the any produce. If aminopyralid has been introduced into your garden, and plants are showing symptoms of herbicide damage consistent with aminopyralid, but produce a harvestable yield, these inadvertent aminopyralid residues are at a level low enough that you can eat the produce from the garden. Produce from the garden cannot, however, be sold. Keep in mind, however, that there may still be contaminants in the manure used (e.g. bacteria such as E. coli) that you need to consider in making your determination of whether to eat the produce.

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Q: Can I allow horses or other livestock into fields treated with aminopyralid?

Yes, but you must follow all labeling and use directions.

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Q: Can I allow pets into fields treated with aminopyralid?

As a standard best management practice for any herbicide, people and pets should be kept out of the field until the spray has dried.

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Q: Will all my plants be affected by aminopyralid residues?

No. Only sensitive plants, including peas, beans, and other legumes; carrots; sugar beets; potatoes; tomatoes; lettuces; and spinach. Dahlia and a few species of rose also are affected.

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Q: What are the symptoms of aminopyralid damage on sensitive plants?

Symptoms can be cupping of leaves, stunting of plants, and curling of the growing point, giving it a fern-like appearance. However, keep in mind that other factors or herbicide products also can produce similar symptoms.

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Q: What level of aminopyralid is harmful to sensitive plants?

This will depend on the species, but aminopyralid can affect sensitive plants at very low levels.

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Q: I have used manure in my garden, and some of the species listed above have been affected, while others have not. Is aminopyralid the cause?

If peas, beans or potatoes (the most sensitive crops) are not affected, it is unlikely that aminopyralid is the cause since it should have affected all of the sensitive plants.

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Q: How can I determine if there might be aminopyralid residues in the manure I purchase?

Ask your manure supplier if the manure came from a farm or equine business where a product such as Milestone® herbicide has been applied, or whether the animals that produced the manure fed on forage (e.g., hay or silage) that came from grass treated with an aminopyralid-containing herbicide, such as Milestone, Milestone VM, Milestone VM Plus, ForeFront® R&P, Chaparral, GrazonNext, Opensight or CleanWave herbicide. If the answer to these questions is no, then it is not likely that the animal manure contains aminopyarlid.

You can also use a bioassay test for the soil, manure or compost, with a sensitive plant or crop.

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Q: How is aminopyralid broken down?

Aminopyralid is broken down by soil microorganisms, which thrive in damp and well-aerated soil. These conditions are best achieved by watering to moisten the soil and rototilling or turning the soil.

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Q: I used manure containing aminopyralid in my garden this year. What should I do?

The best way to reduce the likelihood of any adverse effects next season is to keep the land turned over to aerate the soil, which encourages breakdown of the cellulose material in manure. As it breaks down, aminopyralid is released into the soil and then broken down by naturally occurring microorganisms.

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Q: How likely is the manure I have purchased to have aminopyralid residues in it?

Reports of aminopyralid residues causing problems in gardens have been very rare in the United States.

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Q: Can manure containing aminopyralid be used in the garden?

No.  Affected manure must not be used on gardens where sensitive crops like potatoes, beans, lettuce and tomatoes are likely to be grown.

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Q. Does aminopyralid break down in a rotting manure heap?

No. Aminopyralid will be stable until it is released from the plant cellulose and comes into contact with microorganisms in the soil. Breakdown occurs after manure is incorporated into aerobic soil.

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Q: What can I do with affected manure?

You can return it to your source of supply. Or, you can supply it to a local farmer for use on rangeland, permanent pastures, wheat fields or field where grass is grown for seed.

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Aminopyralid Fast Facts

The following are general facts about aminopyralid-based herbicides. For additional information, please click on the most relevant link on the left.


Aminopyralid does not pose an unreasonable risk to humans or animals when used in accordance with label directions.

  • Aminopyralid has an excellent health, human safety and environmental profile. The U.S. Environmental Protection Agency, along with regulatory agencies in other countries, has determined it does not pose an unreasonable risk to human or animal health when used in accordance with label directions. In fact, aminopyralid was reviewed and registered by the U.S. Environmental Protection Agency under its Reduced Risk Pesticide Initiative.
  • If your garden plants show symptoms of herbicide damage consistent with aminopyralid residues, but the garden produces a harvestable yield, then you can eat the produce because the residues will be at a very low level. However, do not sell the produce from the garden. And before deciding to eat the produce take into consideration other contaminants in fresh manure that could have damaged garden plants. While livestock manure is a natural garden fertilizer, it can include contaminants such as E. coli bacteria, other microorganisms, salts, metals, other herbicide residues and weed seeds.
  • Animals fed grass/forage that may contain aminopyralid residues are unaffected from its use.

A limited number of plant species are sensitive to aminopyralid residues.

  • Sensitive plants include peas, beans, potatoes, sugarbeets, carrots, tomatoes, lettuce and spinach..
  • Manure that may contain aminopyralid is labeled for use on rangeland, pastures, or fields where wheat is or will be grown.

Aminopyralid breaks down in the soil

  • Aminopyralid breaks down through the action of microorganisms in the soil over the growing season and in many cases dissipates by the following year.
  • Residues in manure may break down more rapidly if the soil on which it is applied is rototilled or turned frequently — but do not use manure that may contain aminopyralid where sensitive crops (listed above) are to be grown even if it is rototilled.
  • A bioassay test can be used to test garden soils, manure or compost for aminopyralid residues.