[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. :-(. )