I can imagine all the work for 8 sago palms. Other gradeners have mentioned scale on their plants in Florida. We do not have that problem in southern CA. I think the humidity in Florida is one reason, but also have you made sure sparklers are not watering on the trunks, foliage and the center of the flushes? Trapped water in the woody frond cuts may be making the problem worse. Check and see if the trunks remain dry the whole summer.