Notice for allotment holders and gardeners

We have been receiving enquiries from people who appear to have observed unusual growth patterns in a variety of crops such as potatoes, peas and beans.  Some callers have enquired whether this may be due to potential herbicide residues in manure.

Dow AgroSciences' grassland herbicides are used by livestock farmers for the control of injurious weeds such as docks, thistles and nettles. It has long been known that it is possible for low levels of product to be found in manure and that the use of such manure as a fertiliser or compost may, in some circumstances, cause damage to sensitive crops. Where this potential exists, Dow AgroSciences' products carry warnings and advice.  When using any herbicide product, the label advice and safety instructions should always be followed.

In response to whether crop damage may have flowed from the application of, manure containing herbicide residues, we thought that the following examples of some the questions we have been asked may be helpful. 

You can also contact us by email at UKHotline@dow.com  if you have any specific questions.

Can I eat the affected crops?
How do I deal with the affected areas to help remove the risk of plant damage for future years?
What do I do with any remaining manure?
Can I replant this season?
Why does your chemical last so long?
How do I avoid this happening again?

Can I eat the affected crops?

Aminopyralid has very little inherent toxicity to people or animals and consumption of affected crops would not have any effect on human health. PSD has now assessed additional information and confirmed that using manure, which may contain residues of aminopyralid, does not have implications for human health  http://www.pesticides.gov.uk/garden.asp?id=2480.

The data shows that using worst case assumptions the residues would not cause concern and while the product is not authorized by UK regulators for use on food crops, these crops can be eaten.

Aminopyralid has been approved for use on certain food crops in Canada, the United States, and other counties. We are seeking approvals for several food crops in a number of European countries in the near future.

The Pesticides Safety Directorate is an agency of the Health and Safety Executive. One of its duties is to ensure the safe use of pesticides for people and the environment. The procedure for approving pesticides for use in the UK is rigorous, each approval requiring scrutiny of extensive safety testing. All of Dow AgroSciences' herbicide products which are offered for sale in the UK are approved by the Pesticides Safety Directorate.

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How do I deal with the affected areas to help remove the risk of plant damage for future years?

In our view, rotavation is by far the best practice. This incorporates plant tissue into soils where it will decompose and allow the associated chemicals to be degraded by soil microbes. Once degraded, the chemicals should pose no further risk to crops.  Ideally, thoroughly rotavate, or fork over several times as soon as possible, then repeat in late summer/ early autumn. Plant tissues generally break down most rapidly in warm, moist soils.

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What do I do with any remaining manure?

If you believe that the manure or compost you are using may contain herbicide residues, it should NOT be spread on ground intended for food crops.  Sensitive crops include peas, beans and other legumes, sugar beet and fodder beet, carrots  potatoes, tomatoes, lettuce and a number of other food crops or edible plants.

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Can I replant this season?

We would not recommend replanting this year. The ground needs to be thoroughly rotavated and plant residues given time to break down.

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Why does your chemical last so long?

Our products work by binding strongly to plant tissues, as do other herbicides.
Once plant tissues decay, breakdown of active ingredients in soil should happen very quickly under normal conditions.

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How do I avoid this happening again?

Before accepting any farmyard manure for use in your garden or allotment, it is always important to ask the supplier for confirmation that it does not come from livestock  which has grazed on fields, or been fed fodder, that has been treated with herbicides bearing restrictions on the use of subsequent manure.  Any Dow AgroSciences' product with potential to cause such an effect (e.g. those containing a substance known as aminopyralid) carry warnings on the product label and specific directions as to appropriate conditions of use. If your supplier's livestock were fed with grass, hay or silage produced elsewhere, then you should trace back to the original grower to obtain this information. 

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