Thanks for your question.  You are correct that there may be many possible causes.  The simplest one, given the information you provided is something called herbicide drift.  In short, have you and/or your neighbors applied any herbicides to lawns or gardens within the the past week?

Looking forward to your response.



Thanks for your response,  I should be able to get back to you by tomorrow (8/4).

Thanks for your patience.

Thanks for your patience.

I do not have a single, good answer to your question having ruled out herbicide drift. There are so many possibilities including:

1). Both overwatering and underwatering can cause leaf curling and yellowing. Ensure that your soil is consistently moist but not waterlogged.

2). High temperatures can cause leaf curling. Considering how quickly this condition came on, I think this is a good possibility.

3). Numerous pests/diseases may be causing this. These include aphids, spider mites, white flies, and cucumber mosaic virus. If you want to pursue this possibility, you may want to submit some plant materials to the University’s Plant Disease Clinic. See the following:

https://extension.umn.edu/plant-diseases/insects-and-diseases-cucumber-pumpkin-and-squash

https://extension.umd.edu/resource/key-common-problems-cucumbers/

https://extension.umn.edu/disease-management/downy-mildew-cucurbits

https://pdc.umn.edu/

4). For the immediate present, I would suggest that you remove and discard all yellowing leaves. Keep things well watered. At this point it would be difficult to predict what type of cucumber crop you can expect.

Good luck. I’m sorry to be so general in my response. Please get back to us with any further questions you might have.