Q.My Very Heathly Cucumber Plants That Were Fruiting Suddenly Started To Develop Yellow Crunchy Leaves And A Rotten Stem.
I cannot see any sign of pests and the roots seem okay. Could it be linked to overwatering and drop in temperature
Certified GKH Gardening Expert
Yes. Overwatering, with a drop in temperature is the perfect recipe for infection. Unfortunately, without seeing the damage in question, it will be quite difficult to say what it is, exactly.
Most broad spectrum fungicides will take care of the issue, but it will likely be next year's crop that will be unaffected. Treatment will take a little while to work, so right now would be a good time to treat for next year's planting.
Here is an article to help you with fungicide use:
Here is an article that will help you with proper care of cucumber plants: