Answer: Insecticidal soap is a contact insecticide so it won't hurt the predators unless you spray it directly on them. The soap is only effective on the scale when it is in the soft juvenile stage and you will also need to contact each one with it. You can try physically removing the scale by hand although it is a seemingly impossible task to find them all, even with a bright light. It seems like scale populations skyrocket every spring, so it pays to keep a very careful eye and start a routine with the soap as soon as you notice the activity each year; eventually it does lessen.
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