Greenhouse fumigation - RSMites

Hi,

Loosing the battle with the Red Spider Mites in our greenhouse so was looking to do a deep clean once the toms have finished.

There are several smoke bombs on the market but no idea how effective they are.
Appears the DeadFast on can be used with the plants still inside, but others like Battles Sulphur need them removing. Not sure about the Vitax on.

Any recommendations of the smoke bombs and any other cleaning preparations that will help reduce these little critters.

 

As someone who has been battling RSM for the last 30yrs all I can suggest is that unless you throw all your plants away it will be a waste of time.
The eggs over winter on your plants not so much the greenhouse.

Got to say I've not tried recent smoke bombs, but the old ones never seemed to work.

 

Good point @pete, doubt any smoke bomb would affect the over wintering eggs ..

Have been using Bug Clear Ultra spray which is contact and systemic, but you need to be very diligent in its use otherwise they are straight back and with getting older its too easy to loose track !

Often wonder if the eggs or adult survive / hide in the top layers of the compost, so giving the pots a drench of insectiside, like for vine weevil, would be worthwhile ?

Some suggest Nematodes but equally admit they will only reduce rsm, not erradicate them.

 

I've tried biological methods, not nematodes, but another called persimillis, very expensive to keep introducing and doesn't work below certain temperatures.
Good for commercial growers but never found them much use myself after a few years of trying.

I've even tried animal sprays that kill mites but I dont think they would be good on sensitive plants.
If you even consider the cost of preditors then this could be an option, but its not cheap, but it seems to work.
Insecticide Nurelle D 100ml | Pet Drugs Online

 

Pyrethrum is said to be effective, either as spray or powder. It could be applied to plants, soils and surfaces, cracks and crannies. Avoid breathing it in a confined space such as a greenhouse.

 

You could try Neem Oil. It's very popular in America and is starting to make itself known here now.

 

It is my understanding that the use of neem oil as a pesticide is illegal in the UK. From memory, I think it’s to do with the active ingredient (azadiractan - or something like that) being detrimental to pollinators and injurious to human health.

 

Yes, you are right @Ezzie, think it will surprise many as its always been made out to be natural and safe.

Seems its not just Azadiractan that is the nasty part of it, many other undefined elements as well.

Interesting info here -

Azadirachtin - Wikipedia

https://bobcutmag.com/2021/09/10/why-is-neem-oil-banned-in-uk/

 

Natural products tend to have undefined/ill-defined compounds in them, they also vary from batch to batch, season to season and with growing conditions. That's why Australian Chardonnay tastes different to French Chardonnay and why teas are blended.
As for Neem Oil nothing I've read would deter me from using it in the garden as a pesticide. May be when my current bottle of Organic Pesticide is done I'll go with Neem.

 

RSM used to be a problem mostly on greenhouse plants, but it is becoming more of a problem on outdoor stuff.
My Crocosmia lucifer flowered badly this year and went totally brown, but when I looked it was infested with RSM, likewise a Leychesteria plant, totally brown and dead looking, without close inspection you would blame the heat, but that was only part of it, the RSM did the rest.

A plant of Musella was also covered in them, that had been outside since April.

They were reporting that autumn had come early on the news yesterday with trees losing yellow leaves, blaming the drought, I do wonder if anyone has closely looked at the undersides of the leaves before coming to that conclusion.
Could be drought, I dont doubt, but I bet insect attack is playing a part.

 

I grew tobacco a couple of years ago and brewed up my own nicotine insecticide.
Scared to use it now, haven't got a clue about dilution rate etc.

 

What the devil is RSM please?

 

Red Spider Mite.
Tetranychus urticae - Wikipedia

 

Thank you @pete. Silly me didn't look at the first post

I use neem oil or a spray with spinosad. Neem is the cheaper for me so that is usually my go-to.

I've found that since I put fans in the greenhouses, it has cut down considerably on the number of times I've had to battle those nasty mites. Both of those things also worked on the white fly that invaded. Unfortunately I applied it a bit too late on most of my chillies.