october

Hello Treetitan,
I have responded to several scale problem posts in the last week or so. Unfortunately, I know alot about this subject. First you must know your enemy. There are different types of scale. White small rice looking juniper scale, oyster shell scale ( looks like tiny oysters the size of a pencil's eraser) and brown oval soft bodied scale. I have been battling scale for over 3 years and finally have one up on them.
Scale suck the juice from a tree until its dead. They have a piercing part of their mouth for this. As they age, they secrete a fluid. Each time they secrete, they build up a protective shell until they are almost immune to pesticides. Also, they lay their eggs underneath this protective shell. So even if you pull them off, the somewhat invisible eggs are left behind.
First isolate the afflicted tree/trees. If you use the dunking the pot watering method, do not put another tree in the same water. Also, do not mist that tree where the mist will go onto another tree. Scale will attack your whole collection, starting with fruiting trees. Scale eggs can be spread through water, wind and ants carry the eggs as well.
My advice, from my experience is, first pick off all the scale you see. Then use a horticultural oil. Read the directions. You will probably have to use the maximum amount for the tree species. Then check the tree in 3 weeks and pick off anymore scale, then spray again. Then for the next 3 months, spray about once a month to once every month and a half. You can substitute one of the months spraying with a systemic, instead of the oil. However, you may notice that after a couple of months the scale may be almost gone. The oil smoothers the insects so thay can't move or breath.
Keep in mind that you will have to pick even the dead scale off the tree. The difference between live and dead is that the dead ones just flake off, the live ones smear and bleed. Scale can be one of the toughest insects to irradicate, good luck.