By Matthewj
United Kingdom 
Hello Gardening questions
My cucumbers in the greenhouse developed yellow leaves, which progressively turned to brownish/red, then curling up and dying. The leaves and around the supports became covered in a cobweb effect which led to brownish trails leading off the edges of the leaves. There are no obvious bugs but in the cobwebs I can see under a magnifying glass tiny white specks which I presume are larvae. Please, any suggestions?
Thank you.
Matthew
3 Aug, 2014
Answers
Hi, welcome to GoY, yes I agree with Cammomile, this is typical of red spider, Derek.
3 Aug, 2014
Yes, I can't grow cucumbers in my greenhouse either. I have tried spraying and damping down but have resorted to growing outside in pots. Tomatoes like the heat but cues do better in a cooler and very damp situation. I even tried SB Plant Invigorator (as suggested on Radio Kent Gardening) in desperation but with little success.
4 Aug, 2014
Each time I discovered the problem, I sent off for some biological (bugs) which eat the mites but it was too late by the time they arrived. The plants were decimated in a matter of days.
4 Aug, 2014
Thank you for the helpful replies.
Matthewj
5 Aug, 2014
Red spider mite. I got this every year when I grew cues. By the time you realise you've got them its usually too late. You need to keep the greenhouse dampened down by watering the floor daily.
3 Aug, 2014