[DorsetDear]

Our hay field is slowly becoming a thistle field and other small paddocks thistles are competing with grass. We need to spray them. My partner would like to do it safely with a knap sack. What courses does he need to do? Is it PA1? I think I've found someone that provides the course online. Has anyone done it?

[SallyintNorth]

I can't help you with chemicals, sorry, but just in case it's useful to you or to other readers...

Top them in July, every year.  (You want them in flower but not yet gone to seed.  "July" usually works!)  You won't recognise the field within a couple of years.

Untreated cut thistles are highly palatable to livestock, or if you flail them all the nutrients will feed the ground for future years.

[Fleecewife]

Which kind of thistles are they?  Spear thistles or creeping thistle?  Spear thistles need to be dug out by hand or sliced below ground just before the flower is about to open in June or July, creeping thistle is dealt with by frequent mowing.  So much safer than using poisons, which I can't advise about.

[Rosemary]

I support both Sally and Fleecewife. We had a huge thistle problem, started topping just before they set seed, when they've expended most energy and we have ahrdly any now. I did buy spray but it's in the shed.

[Penninehillbilly]

I've been using a Ragfork for thistles, time consuming but satisfying. I had them down to just a few, but couldn't do it for a couple of years, as bad as ever this year. I try and let butterflies and bees have a go at the flowers, then get them before they seed, so timing is critical.
I don't like the idea of using weedkiller where animals graze, unless no option. (Spot treating to reduce the rushes. :-(. )

[twizzel]

Think you need PA1 and PA6. Or alternatively find a contractor to spray them.

[Lambic]

For what it is worth.

I have used Grazon on my place, in an epic battle against docks.  Spot spraying with Stihl battery powered backpack.

Unbelievably I have won, after 2 years.  Many thousands of them dealt with.

Grazon is highly effective.  It also works on thistles and nettles

It will also too expensive

Last week I finished my 5L of Grazon and have now bought 5L of depitox.

If you mow the thistles strategically, especially before flowering, they will eventually give up.  Basically get the plants to expensive asucj energy as possible, then chop and drop as green mulch before going through seed

[Lambic]

My limited understanding is that you do not need the training certificates to buy the nuclear strength products, but you are supposed to have them too apply the product.

The chrmicals should be avoided at all costs really, but sometimes it just has to be done. 

I apply as little possible and extremely cautious near my ponds / burn / ditch.

We literally have 100,000s of amphibians because of the pond network. They are very sensitive to pollution, as are my trout

[SallyintNorth]

Also be aware, if you are using Grazon or similar on mowing land, or grazing land for horses and you poo pick, that the broadleaf plant killers in it are mega persistent.  They will survive haymaking, silaging, digestion and composting, and if any rotted FYM or other material ends up in your veg plot will kill - or at least stunt - all the broadleaved plants you are trying to feed. 

Cattle farmer I knew had given up trying to grow turnips after repeated failed crops until we fathomed out he Grazoned his most thistley mowing field, fed the silage he made to the cows, spread the muck back on the turnip field...