What is this please, and has it killed my bean and cucumber?

Like Pete, I've struggled with it for years too. This year is the first year that my greenhouse (conservatory before that at my old house) has been RSM free. I bleached it last November (very strong solution) using a pressure sprayer.
I've used parasitic mites with great success, but once the mites are gone they die out. They will die over the winter anyway so you need to buy new every time anyway.
Small plants can be treated effectively by giving them a repeat blast of Vick Vapour Rub dissolved in boiling water. Place a saucer topped up with gravel in the bottom of a clear placcy bag, pour the mix into the saucer to BELOW the top of the stones, put the plant on top and then seal the bag. Place in a warm spot for 6 to 8 hours and choke them to death. Repeat every three days for two to three weeks (long enough for any eggs to hatch). It works.
On plants with large leaves wipe the leaves top and bottom with a fairly strong w/up liquid and water solution. Less of a cure, more of a control measure. Try one leaf first to see if it has a bad affect on it foe a few days.

I agree. Last year my Cantua was affected, this year I have an Erythrina seedling affected.

Not here they don't!

 

I thought red mite live on birds and spider mites plants , I may be wrong

 

They do................

They do, but................

You were!
Red spider mite is a species of spider mite, not red mites (which are particularly attracted to chickens IIRC).

 

Thank you for breaking that down for me , made it so much easier to understand

 

@LindsayH , I'd be interested to know in what way your dog reacts to these chemicals.

Must admit over the years I've used all sorts on my plants, but never thought there was anyway it could affect my dog at the time.
I obviously always kept the dog well away while I was spraying and usually until the spray dried, especially with weedkiller.

In fact my last dog used to go indoors immediately, of her own accord, when she saw me get the sprayer out .

 

What about foliar feeding your plants? Might help slow down the mites if they don't like fertiliser chemicals?

 

Foliar feed may help the plant fight off the invasion somewhat, but the fertiliser won't impact the mites at all.

 

I love this, my collie does this at home when I get the mower out and at the stables when I get my horse's saddle and bridle

Symptoms vary depending on the drug, and the dog. My dog has had tremors, ataxia, lethargy, dilated pupils, off food etc. It can literally be anything from a tiny bit quiet through to coma!

My parasitic mites have arrived already!

 

Well, I applied my (hopefully ferocious) Phytoseiulus predator mites. In case anyone is interested I got them from www.defenders.co.uk. They arrived very quickly and I could see lots of them crawling about energetically in the tube. They replied to an email I sent to them asking for advice after I received them very quickly, they compared favourably price wise and they do lots of different biological controls.

 

Possibly. Got a close up?

 

I would say so fat controller

 

I'm afraid that it certainly sounds like it FC.