Young Leaves Curling and Turning Gray
I just transplanted some cucumber and zucchini plants in my garden about a week ago. I have noticed the leaves are curling down and turning a grayish color on the ends. The weather has been cool and rainy being Washington State. So I'm not sure if they are getting too much water or if it is shock from transplanting. If it is too much water, should I bring them back in the house or do something to cover them up somehow? This is my second year having a garden and my first year starting the plants from seeds so I'm still learning the different signs of health issues.
Based on the symptoms you described as well as taking into account the rainy weather, I would say that your plants have powdery mildew. Powdery mildew is gray in appearance and can cause leaves to curl. For more information on powdery mildew and a course of treatment, please visit the following links: