Answer: Some transplant shock is to be expected with a new tree, so a few dropping or yellowing leaves would not be unusual. However, leaves that are turning white indicate either a severe soil pH problem, or a fungal disease called powdery mildew. Citrus are not usually affected by this fungal disease, especially if they are planted in full sunshine and have good air circulation all around. Just to be sure this is what you're dealing with, take a few of the affected leaves off your tree, place them in a plastic baggie and take them to your local nursery or cooperative extension office for a positive identification of the problem. Helpful folks there can suggest control remedies.
Best wishes with your orange tree!
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