Question
My leaves are turning white and I do not have a mold or a fungus.  I have a hydroponic garden and I spray with organic materials.  The leaves started turning white, and then the veins in the leaves.  Eventually the leaves are going completely white.  I checked for squash beetles but there aren't any.  Help!  I do not want this to "travel on" to my other vegetables.  

Answer
Elizabeth, if you have definitely ruled out a fungus disease, the most likely cause of leaves blanching or turning white are lack of sufficient sunlight or excessive watering. Since I assume the plants are getting light, make sure you limit watering to 1" per week. I also recommend mulching around the plants with organic matter such as straw or dried grass clippings to cool the soil and retain moisture, which then limits the need for watering.

Another possibility is that you have an insect infestation, such as aphids, that may be sucking at the plants. You could try spraying with an insecticidal soap. If this does not take care of the problem, you can resort to pyrethrum or rotenone, two organic insecticides. You can check the leaves with a magnifying glass to confirm that insects are the problem.

I would start with these recommendations. If you still have the problem, please write again.

Good luck.

Mike