My sago has white things (about 1 mm, less than 1/16 in.that look like dashes - - - - ) covering the leaves, bottom and top, and in some areas on the stems of leaves. In some places they are mixed in with tan/brown material, forming a covering that is so complete you cannot see the green leaf stem unless you brush it off with your finger. Is this your typical scale that needs to be treated with an oil? Should all the leaves be cut off, including baby ones coming out of the ground (which also have these white line things)?
Sago Palm Pest
Certified GKH Gardening Expert
It does sound like it is scale. Treat the leaves and leave them on the tree. While they may look unsightly until new leaves grow in, the plant needs them to help it remain healthy and to produce energy while it is growing new leaves. This article will help you with the scale: https://www.gardeningknowhow.com/houseplants/palms/sticky-palm-tree-leaves-treatment-for-palm-scale.htm