Question
we have white scale what is the best spray to use and how often?

Answer
It is best to treat with a product called Bayer Advanced Tree and Shrub Insect control. It is applies to the soil around the shrub and the roots will carry it to the twigs and leaves and when the insects suck the plant juice they are killed. This will give you season long protection.  Check with your local garden type store for this product. Here is a web link to the product. http://www.bayeradvanced.com/tree-shrub-care/products/12-month-tree-shrub-insect...