My Camellias have some white dots on the undersides of the leaves and some yellowing from it too. What is causing this and how do I stop it?

What you see on your Camellias are Tea Scale. Tea Scale can be safely and effectively controlled by spraying thoroughly with SunSpray Ultra-fine Oil. This oil is safe to spray all year long. Many other oil sprays should not be used in hot weather, but Sunspray can be relied on even in our summer heat. This product kills by smothering instead of poisoning and can be very effective by repeating the spray treatment about 3 weeks after the first treatment.