A free pdf of the new Cucurbit Disease Field Guide: A Disease Reference Guide for Cucumber, Melon, Squash and Watermelon (Disease Guide Final 010715) is available. The guide was produced by Monsanto Vegetable Seeds/Seminis/DeReuter. This 122 page guide has lots of great pictures of cucurbit diseases to assist in diagnosis. Consider uploading this guide on your smartphone, iPad or tablet to take into the field.
Cucumber leaf with downy mildew symptoms