Answer: It is probably powdery mildew fungus. This disease can be a problem on peas and certain other vegetables. One organic option is to spray the plants with a labeled product containing neem oil (not just the ingredient azadirachtin, but the oil of neem). Another option is to use a labeled product containing either potassium bicarbonate or sodium bicarbonate (baking soda).
The following web site contains a great deal of information on the bicarbonate sprays including source of these products:
Q&A Library Searching Tips