Question
I have 4 Burning bushes next to each other.  Overthe the wintee they developed something on the branches.  It's white in color and cottony in texture and I can easily rub them off with my finger.  I looked up scales, but it does not fit what I have.  I have another set of 4 sepeated by an A/C unit which have nothing.  Not sure if this is harmful and before I start assuming and purchasing chemiclas I wanted to know if you had any ideas/

Answer
It could be one of a couple of things--there is a woolly aphid that is covered with a white cotton like substance. If you touch them they should move. The aphid suck the plant juices from the plant and secretes a waxy material that is white. You should be able to see some of them moving if you shake the plant and look close. You should also feel the leaves and they should be sticky with a honeydew from the aphids.
These can be controlled with the use of an insecticide called Bayer Advanced Tree and Shrub Insect control It is applied to the soil around the bush and the roots transport it to the stems and leaves and when the aphid sucks the plant juices it is killed. Your local nursery/garden type store will have this product. Here is a web link to information on this product. http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html

IF it dose not move it is a fungi called powdery mildew. It can be controlled with the use of a fungicide. Powdery mildews, as the name implies, often appear as a superficial white or gray powdery growth of fungus over the surface of leaves, stems, flowers or fruit of affected plants. These patches may enlarge until they cover the entire leaf on one or both sides. Young foliage and shoots may be particularly susceptible. Leaf curling and twisting may be noted before the fungus is evident. Severe powdery mildew infection will result in yellowed leaves, dried and brown leaves and disfigured shoots and flowers. Although it usually is not a fatal disease, powdery mildew may hasten plant defoliation and fall dormancy and the infected plant may become extremely unsightly.

To control this fungus spray the foliage with a fungicide.
Fungicides must be used to achieve acceptable control. For best results with fungicides, spray programs must begin as soon as mildews are detected. Spray on a regular schedule, more often during cool, damp weather. Use a good spreader-sticker with the fungicides. Be sure and cover both surfaces of all leaves with the spray. Fungicides generally recommended for powdery mildew control include: Triadimefon (Bayleton, Strike); Triforine (Funginex), Thiophanate-methyl (Cleary's 3336, Domain) and Propiconazole (Banner).

Here are a couple of web sites that discribe cottony aphids and powery mildew with pictures.

http://www.ca.uky.edu/entomology/entfacts/ef219.asp

http://ohioline.osu.edu/hyg-fact/3000/3047.html