Scale has got to be one of the most difficult to control insects that I have ever encountered. I have never been able to make one or two applications and been able to just walk away.
I also must take into consideration that I am using an organic insect treatment and though these products are extremely safe they tend to move rather slow not to mention it's more like a 6 or 7 application process. I am just now noticing that the population is declining however I have been fighting these guys for months.
Both my Sasanqua Camellia and Heritage River Birch always seem to have scale. The River Birch will get mealy bugs too towards the end of the Summer into the Fall
Sasanqua Camellia


Heritage River Birch

The product that I am using contains .10% Sesame Oil, 1.84% Edible Fish Oil, .6% Lecithin and the remaining 98% is water.
Again, this is an organic product that moves very slow. It kills on contact and doesn't have much of a residual therefore the insects MUST come in contact with the insecticide.
If the infected plant(s) are more than 25-30% covered with scale I would use something stronger like Tal-Star, Merit or Conserve. These are non-organic and also kill beneficial insects like bees, ladybugs, etc. so if you have to go this route then READ THE LABEL and mix accordingly. Again, use this product very sparingly because of the environmental/safety risks. There is a certain threshold that you must learn to accept and manage.
Location:Effingham Cir,Raleigh,United States