Cucumber mould on stem

I have a couple of Passandra cucumber plants and one (plant one in pics) at first had wilting bottom leaves that went yellow, but the remaining leaves being ok and producing fruit. I then noticed a fungus mould at one of the branch node points so I have cut the plant off below the mould and hoped for the best. Plant two is producing fruit but showing first signs of the same. Has any one got any ideas on what the problem is, is there a treatment?

Thanks
Richard

 

Advice taken and will act upon.

Thanks
Richard