Question
will volck work on sago palms to destroy scale

Answer
HI Pat..
It could possibly be Asian Cycad Scales. Asian cycad can be very damaging to plants if left untreated or allowed to spread. If you have sago palms, monitor the plant and check for white, cottony scales along the veins, stems, and leaves. If you do not have a heavy infestation start by clipping infested branches (fronds) and destroying them. In heavily infested palms it is impossible to clip the branches because you would be clipping each one.  You could try different types of fungus sprays and you may find one that works.  

If you do not have the Asian strain, sago palms seem to always have the fungal problem and you will be having to keep on eye on it always.  Now with this new strain I have read that eventually all sagos will be dead in Florida.

Most websites suggest to just kill the plant as there is no good treatment other then waiting for a natural enemy of these insects to get high enough population in Florida - this insects come from Asia.