Most of the leaves on my cucumbers look like the picture below. What is the problem? My first guess is some kind of fungus. Can anyone identify it and recommend a treatment.
What's ailing my cucumbers?
Definitely not a fungus. Looks like cucumber mosaic virus, although I'm not a veggie expert so maybe there are other problems that have similar symptoms http://gardening.about.com/od/gardenproblems/ig/Insects-and-Diseases-of-Plants/Mosaic-Virus.htm
If its on the plants around your cucumber and on other plants in your garden and they're is webs then i'd say its mites. That can be cured by 50:50 water and rubbing alcohol, but dont go past that because it also kills other things that may benifit. If you do do that make sure you get under the leaves. Mites also hate dampness.
I don't think it's spider mites--the stippled yellow pattern you see from them is typically a much finer pattern (smaller yellow spots). Doesn't hurt to check the underside of the leaves though just in case--you'd see them as little teeny tiny reddish or brownish dots.
Easiest way to check for mites: hold a sheet of white paper under a leaf, flick the leaf with your finger, check paper for little "specks" that move. If you use a magnifying glass you can tell if they are two spotted mites or some other kind.
The leaf symptoms look to me like a mosaic virus, not mites. If it is a virus there is no cure. If you leave a virused plant the disease can be spread with tools, by touching it and then touching a healthy plant and by aphids and/or cucumber beetles.