You say there's no sign of insect pests but my cuke plant leaves look like that after being infested with cuke beetles and squash bugs. The cuke beetles spread a wilt disease which finishes off the plants. Best guess.

I've gotten hit with that before, whatever it is. Enjoy the cukes now -- your plants will be toast soon.

I'm seeing that this year in my ordinary Armenian cukes. Total devastation. Curiously, my Striped Armenian cukes, right next to these, are untouched. I have to wonder if the latter is a resistant variety.

Alternaria?

Here's link to a list of cucumber diseases with photos...

https://www.lsuagcenter.com/portals/our_offices/departments/plant-pathology-crop-physiology/plant_disease_clinic/disease_image_gallery/herbs_vegetables/cucumbers/cucumber-diseases

Google Image search is my friend - I just put in 'cucumber diseases' and lots of pix show up.

Thanks everyone. I'm 100% sure there aren't bugs. I think it could be the anthracnose or leaf spot. I've planted them in the same area for a number of years, so I may need to move them. Also, this heat has probably decreased its ability to fight off things. I can only grow County Fair cucumbers and they aren't listed as ones that Immune to anthracnose. I wait for 10-12 months for these every year. I love them so much. I make Danish cucumber salad all the time, and it takes a fair amount of them. So I guess I need to prepare for their funeral. :( They really were slow to grow this year. I have an arch made out of a cattle panel and plant them on both sides. In the past they have grown over the top and produced an outrageous (but wonderful) amount of cucumbers. Fortunately my Waltham butternut squash growing nearby hasn't been infected.........but the heat, etc., so far has only produced 1 small squash....with no more females in site. The males are pretty bummed out. ;) Thanks for your help!

Ugh...went out there today and see that now I have it. I might get another 2 weeks or so out of the vines, it's just starting. The charantais melons have it, too. Whatever it is, the melons get it every year but the melons usually ripen by the time the vines die; I hope that is the case this year, I've got a few nice plump ones basking in the sun and surely sweetening up.

Hi carol.....I think there's a whole lot of funky things going on with plants, birds, insects, etc. because of the climate disruption, unfortunately. :(

Mxk........Good luck with your melons. I'm only going to get 1 butternut squash this year. It makes me sad. :(

Just to add. County Fair has gotten hard to find, but Little Leaf is also highly resistant to the wilt carried by the cuke beetle and much easier to find.

laceyvail......maybe I shouldn't share this, 'cause I want to keep getting at this place.....;)...but this year I bought the county fair seed from RH Shumway. Looks like they still have it available. I always buy a couple year's worth ahead of time. I have tried Little Leaf in the past, but it just didn't work as well. I am absolutely addicted to Danish cucumber salad, and have to have cucumbers! Hopefully climate change doesn't ruin it for me. Good luck to you and growing cucumbers.

Hi all. Well, my cucumbers are goners. I'm so sad. They're one of my favorite crops. Whatever that disease was.........it worked fast. I grow these on both sides over a cattle panel arch and usually by this time of year both sides are clear up over the top and I have cucumbers coming out the wazoo......which I love!! I can never have enough cucumbers. Today was the last day for making my favorite Danish cucumber salad. I sliced the last cucumbers while giving them appreciation and thanks while using the last ones. :(

Oh yea...fast it is... Sorry to hear you got wiped out. Mine are still hanging on, but barely. My charentais, too. Dang I would like ONE ripe melon -- is that too much to ask?!?!?!

I planted some late cuke seeds about 8 weeks ago (my early cukes died out 3 weeks ago). Picked the first late cuke this morning and more are setting. Around here starting late cuke and late tomato seeds (around mid-June) are the only way to continue harvesting both into the autumn months. I probably would have picked that first cuke 2 weeks ago but a deer nibbled off the new vining tips before I protected them with fencing, arrg.