Herbicide Spraying, Atypical myopathy and Sycamore

I haven’t blogged for a long time (far too long in fact) and hadn’t really had anything to blog about until today. I was asked to visit a privately owned livery yard by the owner. She had suffered what can only be described as a blanket of sycamore seedlings taking over an area of perhaps 5 – 6 acres. This blog deals with my view on that and also has some information around Atypical myopathy and herbicide spraying in general.

I have (in previous years) sprayed off small areas of sycamore seedlings both with a knapsack sprayer and boom sprayer and felled and removed sycamore trees to reduce the potential for the infestation of seedlings to reoccur on sites (information on Tree Work and Forestry), but had never seen such a large area so densely carpeted in seedlings.

I spent a few hours this evening researching Sycamore seedlings and the effect it can have on horses and ponies. I don’t claim to be a Veterinary Surgeon or a Veterinary Nurse, so the below is purely information I have researched out of interest. I can’t verify how truthful any of the information is, but I see no reason to doubt any of it.

Atypical myopathy is an uncommon, yet often fatal illness usually found in grazing horses, mostly in the autumn and spring, and is still a mystery. The illness weakens the muscles of the body and can present with sudden stiffness, muscle tremors, collapse and colic-like signs, with a low temperature. Often dark urine is seen. The fatality rate is around 70%.

Studies have revealed that toxins from the seeds and seedlings of the tree Acer pseudoplatanus (more commonly known as Sycamore) are the likely cause. The toxin is not always present in every seed or seedling, or in seeds or seedlings from every tree. This makes it difficult to predict whether horses will become ill when the seeds or seedlings are ingested. It is not contagious and can affect horses of all ages and types, but young and very old horses may be more vulnerable. Seeds and seedlings can be tested for the toxin, but the accuracy of any such tests have never been established.

Outbreaks of the disease tends to be seasonal, with most cases occurring in the spring and autumn. It is usually more common when horses are kept in sparse or over grazed pastures; where seeds are on the ground and are eaten when there is little other grazing.

The beginning of the disease can be extremely rapid, with some horses being found dead in their fields. Indications of the disease can include muscular weakness and stiffness, dark urine, Colic-like symptoms, and sweating and trembling. Horses diagnosed early by blood and urine tests can be treated with intravenous fluids and intensive care, but once the signs are present it is already serious.

My advice as a horse owner / equine contractor / certified and trained herbicide applicator would be to fence off areas where sycamore seeds and / or leaves have fallen or where sycamore seedlings are growing and seek advice from a vet and an insured, experienced, and qualified herbicide applicator as to the best method of removing them.

There is a lot of information floating around on the internet (and especially Facebook groups) about herbicide spraying. The key thing to remember is this – Those who use, or cause or permit others to apply plant protection products (herbicides) or who store and/or dispose of products are subject to a number of legal requirements. A landowner or livery ’causes or permits’ someone to apply herbicide if they request herbicide spraying on their land and is subject to the same legislation as the individual physically applying it. The main points that anyone in the equine industry thinking about having herbicide sprayed onto their land needs to consider are below:

  • Anyone who applies pesticides as part of their professional activities must (including those previously operating under grandfather rights) hold a recognised specified training certificate.
  • All those purchasing professional plant protection products must reasonably believe that products are going to be used by someone holding a specified certificate.
  • All application equipment, except knapsacks and hand-held, must from November 2016 possess a certificate demonstrating that it has passed an officially recognised test conducted by the National Sprayer Testing Scheme. Equipment has to be tested on either a three, five or six yearly basis thereafter depending on when the most recent test was conducted and the type of equipment (details are available in the National Action Plan). All equipment must be calibrated on a regular basis.
  • Users, or those who cause or permit use, must ensure that: all reasonable precautions are taken to protect human health and the environment; applications are confined to target areas; and in certain areas (including public spaces and conservation areas) that the amount used and frequency of use is as low as reasonably practicable.
  • Priority is given to particular products where there are risks to water quality.
  • Professional users and distributors take all reasonable precautions to ensure handling, storage and disposal operations do not endanger human health or the environment.

I will always offer to send copies of training qualifications, insurance, spraying records and risk assessments to potential customers. If you are considering having professional type herbicide applied to paddocks, make sure that whoever you request to do it is correctly certified and insured. After all – most herbicides are toxic and it is your horses that will be on the land that they are applied to. Would you want to take that risk?

If they can’t provide copies of training certificates, insurance and don’t seem to be keen on writing out spraying records and risk assessments and don’t appear on the National Register of Sprayer Operators (NRoSO), avoid them! Chances are they aren’t trained or qualified and the consequences of something going wrong (anywhere between a poorly horse and a large scale environmental incident), don’t bode well for anyone!

If you have any enquiries regarding dealing with sycamore, nuisance paddock weeds or herbicide application in general, I can be contacted by emailing matt@acc-contracting.com and will be happy to help.

More information on herbicides and the law can be found on the HSE Website here!

All the best,


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