[Ema]

I noticed some yellowing and spots on some of the achocha plants about 4 weeks ago but never having grown them before I just assumed it was normal. 

Then 2 weeks later I noticed the french beans situated in the same row as the achocha but separated buy runner beans were looking spotty. These photos are from 2 weeks ago:

Achocha


French beans


This week the spotting has spread to the french bean pods




The french bean leaves are yellowing/dying off and spotty (my neighboring plots fbeans are just going yellow no spots)

The runner beans between the achocha and the fbeans are now starting to look infected this week.

The french beans have had it and I will get rid of them this weekend.

Do i need to dig the beans up or can I leave the nitrogen rich roots in place?

Do the runner beans have any chance of surviving? there are still plenty of flowers left on the plant or should I cut them down to reduce contamination in soil etc?

The achocha are still producing like mad and I'm reluctant to cut them down/dig them up 

If this is fungal is there anything I can do to prevent it happening next year? improve spacing?

This is my first year on this plot and it hadn't been used for a good 2 years before so I dont know of previous problems

[Salmo]

The reason why it is not on the achochas is because they are not related to beans.
http://emmacooper.org/blog/growing-achocha

Quote from above
"If you’re into extreme gardening then you might like to try growing achocha’s close relative, Cyclanthera explodens. Also known as the exploding cucumber, the fruits burst open when mature and spray their seeds outwards. Once the fruits have split, they can be used in the same way as achocha. Take care when growing this plant as the seeds are ejected at great speed and could cause eye injuries."

[mumofstig]

The reason why it is not on the achochas is because they are not related to beans.

The OP said it started on the Achocha and seems to have spread to the beans   

It's a mystery to me, sorry 

[Salmo]

Must read more carefully.

In that case I have no idea.

[gobs]

It isn't necessarily the same disease, these spots are rather plant family specific.

The beans look like halo blight to me.

Whatever is up with the Achocha, could well be a different pathogen. If it fruits, I would not worry this late ein the season.

[Ema]

Thanks for your replies I don't have chance to go to the plot at the weekend but will tonight and see how things have progressed. I think the French beans have had it and the canes would be handy else where