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

This is one of the leaves from my French bean that was in a pot in my greenhouse. It is covered in web with little dots in and discoloured/dying leaves and beans. I'm not sure if the leaf discolouration or the web/dots came first. I have now evicted it from the greenhouse but I have a cucumber that was growing next to it that is similarly affected and can't be moved (it's five feet long). I think the bean is a goner but would like to save the cucumber. Does anyone know what's going on?
Thank you - Lindsay.

 

Its red spider mite.

 

Well, webs are a bad sign. Blast it with water, mist with a soapy water mix, squash them, wipe tyem away with a soft cloth. They are just bugs, and they are a bit difficult to eradicate but easy to kill. Look for eggs, too. It won't come close to killing your plants if you keep on top of it. Those can't survive outside btw, so moving the bean was a good idea. Only hotter places and greenhouses are good for them. You find them often in tunnels/greenhouses/indoor grows. Horrible little blood suckers.

 

Thank you both, off to do some googling

 

I've been down and drenched all the plants in my greenhouse with Bayer Natria spray which allegedly kills red mite and is fatty acid based. I have ordered some predator mites. My greenhouse is crawling with the little blighters - I don't even want to go in there. One of my aubergines is also affected and I think my cucumber probably will die, all of the little baby cucumbers on it have died. I think it may be a right off for this year ( ), is there anything I can do to prevent this happening next year?

 

As someone who has battled this pest for the best part of 20yrs I can only say I sympathise with you.
Some over the counter insecticides say they kill them, but I've up to now only found one that actually did, and that went off the market at the end of last season.

People say neem oil kills them, I've not tried, but I've heard it said you need to apply more than one spray, which to me is a really load of messing around, and it probably damages foliage.

The product which worked well contained a substance called Abermectin, sometimes in other products under the name of Ivermectin or Avermectin.
Its a specific mite killer as I understand it.

I'm now using something called "Envidor", I got some off a fruit farmer, its what all our apples and pears are sprayed with.
If you google it you will find its a specific mite killer also, which importantly works on the eggs as well.

I did used to go to the extreme of buying predators, and they do work, but its a slow process, once you get a massive attack, and really you need to introduce more, on a regular basis.
Its also expensive.

 

Neem oil gets rid off spider mite but doesnt on red mite,still dont know what the differance is between them??

 

Thank you for your kind words Pete, as a new gardener things like this can be quite disheartening. It's good to know I'm not alone!
Unfortunately I can't use any of the -mectins as I have border collie and they are extremely sensitive to them as well as many other pesticides. The only thing I can think of is to get my predator mites in early next year and treat regularly. You're right - they are expensive. I will also give the g/h a jolly good clean over winter but as it has a mud floor in places I don't suppose it will make much difference.

 

Blast them to Buggery with water! Soak the hell out of Everything, flood the place and cloth everything. Helps keep numbers down.
They usually hate soapy water too.
You prob need to spend a good hour manually helping them to die.

 

I have spent the weekend drenching the g/h, although I do usually mist in there every day anyway. The good news is that the bean I'd written off looks like it may have picked up a little from being outside. This horrible weather has come along at just the right time!

 

Its worse than that ... you need to repeat spray daily / every other day (including undersides of the leaves etc.) as it's a contact spray, and has no systemic properties. Upside is that I have found that it does work, combined with Horticultural soap [as a wetting agent, but that is also effective on soft bodies bugs too, of course], it does muck up the leaves on some things, definitely on Cucumbers , but the plant will grow out of that which is better than just dying which is the only other outcome with a bad infestation.

Early in the season may not work as they need a fairly high temperature to work. Make sure you have not used any pesticides before employing the predator, as they too will be killed by any residual insecticide of course.

I found them expensive and, on a very bad outbreak, didn't make much difference (I thought they would breed like fury, given the huge available food source!, but it didn't seem like that was the case. Plus they took 2 weeks to arrive, which didn't help ... the supplier said to spray with SB(??) Plant Invigorator in the intervening period, to keep the plants on Life Support, not sure if that worked either, although clearly that combination is a recognised solution)

Snap

I suggest not overdoing that. Drenching everything is not going to achieve much, but keeping the humidity up will. Drenching everything over prolonged period will wash out the nutrients
and give them wet feet - and Cucumbers particularly won't like that.

 

I had a border collie and I never spayed her with the stuff.
I know you can get it for animal use, but this is for plants.

They overwinter on your plants, mostly as eggs, but in a warm environment they will also survive as adults, like on house plants etc.

They do attack outdoor plants but rarely reach the same infestation rates as greenhouse plants, so often tend to go un noticed.

If you are the kind of person that only grows greenhouse plants during the summer its relatively easy to kill off any that are overwintering, if like me your greenhouse is crammed with overwintering plants, its very likely some will survive till next spring.

 

I think its basically the same thing @joolz68, I was told its a mite not a spider, and most mites appear to build up resistance to chemicals very quickly.
There are a few different species, but RSM, I think. the 2 spotted one is the main one of concern here.

 

Thanks Kristen, thanks Pete!
It sounds like I may be able to get on top of it over the winter then as I only have few plants that move into the g/h over winter and I might be able to do something else with them instead. If nothing else, at least I'm far more aware now and will pay more attention in future when checking the plants on the back of the benches!

As to Macrocylic Lactones (-mectins) and border collies, you should always exercise extreme caution where there is any chance of the two coming together! Collies (and a few other breeds) can suffer from a genetic mutation (of the MDR1 gene) that causes them to be very sensitive to some drugs including macrocylic lactones. They may have one or two copies of this mutation, so may be partly, or extremely over sensitive. It makes no difference what preparation of the drug you're talking about and my dog has reacted when they sprayed the field next door with something, although I don't know what it was. She was also affected when I dosed my horses with a similar drug to kill lice and she went in the stable the next day.
Hence the over-caution!