Cucumbers

Hi all,

Just after some advice. As you will see by the attached, my cucumbers aren't doing too well this year.

Only difference from previous seasons is that I've used half bags of compost rather than grow bags.

I've read it might be iron deficiency? Even the new plant (right) has started to develop same issue.

Any ideas as to cause and remedy ?

Many thanks in advance

Martyn

 

It looks as if it could be red spider mite, have a look under the leaves and you might see some fine webbing and if you look closely small red dots about 0.5 mm in diameter, a hand lens can be useful.
As for treatment they like dry conditions so increase the humidity if possible. The best treatment is to use biological controls, just google red spider mite biological controls and it will flag up a number of suppliers..
Treatment doesn't reverse the damage just prevents/slows the spread.
I also remove and dispose of the worst leaves.

 

Looks like red spider mite damage. I controlled it last year by removing all the damaged leaves and spraying the rest with with neem oil. I diluted about 5ml. oil in 1 Litre with a dash of washing up liquid to help emulsify it. I got a small bottle of neem oil from superdrug but likely you can get cheaper on the web.

 

Personally I think the middle one at least is done for and I'd get it out.

 

Thanks guys , really appreciate the help. I've been down checking and noticed the attached on the underside leaves (pretty small!) - I'm guessing these could be the little blighters?

 

that could be thrips, those are the smallest ones i believe. spider mites are visible to the eye just tiny

all the pests are contagious, the main problem with greenhouses is the predator cycle is disrupted

 

Use a hand lens and count the legs; mites have eight thrips six.
More seriously if you you have a fine webbing between leaves on the back of leaves then it's the spider mites.

 

I do get thrip damage on some plants - herbs especially, but I rarely see any. As soon as the leaf is disturbed they jump and vanish.
Comparing the two, Spider mites are quite round, thrips are elongated.
Thrips can jump, spider mites cannot.
As you have a photo showing the bugs not moving I agree with @NigelJ - spider mites.

They're not easy to treat.
They like it hot and dry, so raising the humidity can help a bit.
Removing damaged leaves will reduce the population.
Neem oil does work quite well - it's not toxic, but glues them in place and they suffocate. But you'd need to use it several times in order to catch new mites that will continue to hatch.
Usual bug sprays won't work as the mites are related to spiders, and bug sprays are formulated not to harm spiders.

If you have other cucumber plants it may be easiest to sacrifice the infected one.

 

There are insecticides that work but most are not suitable for edible crops.
Cucumbers I have found to not like most insecticides anyway.

I did used to have some insecticide that I got from a commercial grower but it's really only supposed to be used by professionals.